Initial Public Offering [Abstract] Initial Public Offering [Abstract] Initial Public Offering [Table] Initial Public Offering [Table] Initial Public Offering [Table] Partner Type [Axis] Partner Type [Axis] Partner Type of Partners' Capital Account, Name [Domain] Partner Type of Partners' Capital Account, Name [Domain] Limited Partner Limited Partner [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Columbia Energy Group Columbia Energy Group [Member] Columbia Energy Group Columbia OpCo Columbia OpCo [Member] Columbia OpCo [Member] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] Over-Allotment Option [Member] Over-Allotment Option [Member] Limited Partners' Capital Account by Class [Axis] Limited Partners' Capital Account by Class [Axis] Limited Partners' Capital Account, Class [Domain] Limited Partners' Capital Account, Class [Domain] Common Units Common Units [Member] Common Units [Member] Subordinated Units Subordinated Units [Member] Subordinated Units [Member] Initial Public Offering [Line Items] Initial Public Offering [Line Items] [Line Items] for Initial Public Offering [Table] Shares Issued, Price Per Share Shares Issued, Price Per Share Contribution of capital from parent Partners' Capital Account, Contributions Partners' Capital Account, Units, Sold in Public Offering Partners' Capital Account, Units, Sold in Public Offering Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Additional Ownership Interest Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Additional Ownership Interest Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Additional Ownership Interest Net proceeds from IPO Partners' Capital Account, Public Sale of Units Net of Offering Costs Underwriting discounts, structuring fees, and offering expenses Payments of Stock Issuance Costs Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest Reimbursement of Preformation Capital Reimbursement of Preformation Capital Reimbursement of Preformation Capital Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis Of Accounting Presentation [Table] Basis Of Accounting Presentation [Table] Basis Of Accounting Presentation [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Corporate Joint Venture [Member] Corporate Joint Venture [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Basis Of Accounting Presentation [Line Items] Basis Of Accounting Presentation [Line Items] Basis Of Accounting Presentation [Line Items] Pipeline Miles Pipeline Length Pipeline Length Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest Merger related transaction costs Merger related transaction costs Merger related transaction costs Employee related Merger transaction costs Employee related Merger transaction costs Employee related Merger transaction costs Impairment of Long-Lived Assets to be Disposed of Impairment of Long-Lived Assets to be Disposed of Statement of Cash Flows [Abstract] Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net Income Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to Reconcile Net Income to Net Cash from Operating Activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Deferred income taxes and investment tax credits Deferred Income Taxes and Tax Credits Deferred revenue Recognition of Deferred Revenue Equity-based compensation expense and profit sharing contribution Share-based Compensation Gain on sale of assets Gain (Loss) on Disposition of Property Plant Equipment Equity earnings in unconsolidated affiliates Income from Unconsolidated Affiliates Income from unconsolidated affiliates. Amortization of debt related costs Amortization of Debt Issuance Costs AFUDC equity Public Utilities, Allowance for Funds Used During Construction, Additions Distributions of earnings received from equity investees Proceeds from Equity Method Investment, Dividends or Distributions Changes in Assets and Liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Accounts receivable-affiliated Increase (Decrease) in Accounts Receivable, Related Parties Accounts payable Increase (Decrease) in Accounts Payable Accounts payable-affiliated Increase (Decrease) in Accounts Payable, Related Parties Customer deposits Increase (Decrease) in Customer Deposits Taxes accrued Increase (Decrease) in Property and Other Taxes Payable Exchange gas receivable/payable Increase Decrease In Exchange Gas Receivable Payable Increase or decrease in exchange gas receivable payable. Other accruals Increase (Decrease) in Other Current Liabilities Prepayments and other current assets Increase Decrease In Prepayments And Other Current Assets Increase decrease in prepayments and other current assets. Regulatory assets/liabilities Increase (Decrease) in Regulatory Assets and Liabilities Postretirement and postemployment benefits Increase (Decrease) in Employee Related Liabilities Deferred charges and other noncurrent assets Increase Decrease In Deferred Charges And Other Non Current Assets Increase decrease in deferred charges and other non current assets. Other noncurrent liabilities Increase (Decrease) in Other Operating Liabilities Net Cash Flows from Operating Activities Net Cash Provided by (Used in) Operating Activities Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Capital expenditures Payments to Acquire Property, Plant, and Equipment Insurance Recoveries Proceeds from Insurance Settlement, Investing Activities Change in short-term lendings-affiliated Proceeds from Collection of (Payments to Fund) Short-term Loans to Related Parties Proceeds from Collection of (Payments to Fund) Short-term Loans to Related Parties Proceeds from disposition of assets Proceeds from Sale of Productive Assets Contributions to equity investees Payments to Acquire Equity Method Investments Distributions from equity investees Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital Other investing activities Payments for (Proceeds from) Other Investing Activities Net Cash Flows used for Investing Activities Net Cash Provided by (Used in) Investing Activities Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Change in short-term borrowings Proceeds from (Repayments of) Short-term Debt Change in short-term borrowings-affiliated Proceeds from (Repayments of) Short-term Debt to Related Parties Proceeds from (Repayments of) Short-term Debt to Related Parties Payments of long-term debt-affiliated, including current portion Repayments of Long-term Debt Payments of capital lease obligations and other debt related costs Repayments of Debt and Capital Lease Obligations Proceeds from the issuance of common units, net of offering costs Proceeds from Issuance Initial Public Offering Distribution of IPO proceeds to parent Payments of Capital Distribution Contribution of capital from parent Proceeds from Contributions from Affiliates Quarterly distributions to unitholders Payments of Distributions to Unitholders Payments of Distributions to Unitholders Distribution to noncontrolling interest in Columbia OpCo Payments to Noncontrolling Interests Net Cash Flows from Financing Activities Net Cash Provided by (Used in) Financing Activities Change in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of period Cash and Cash Equivalents, at Carrying Value Cash and Cash Equivalents at End of Period Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum [Member] Maximum [Member] Columbia Pipeline Group Columbia Pipeline Group [Member] Columbia Pipeline Group Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Subsequent Event [Line Items] Subsequent Event [Line Items] Distribution Made to Limited Partner, Distributions Declared, Per Unit Distribution Made to Limited Partner, Distributions Declared, Per Unit Distribution Made to Limited Partner, Distribution Date Distribution Made to Limited Partner, Distribution Date Distribution Made to Limited Partner, Date of Record Distribution Made to Limited Partner, Date of Record Business Acquisition, Date of Acquisition Agreement Business Acquisition, Date of Acquisition Agreement Business Acquisition, Unit Price Business Acquisition, Share Price Daily Distribution Rate Daily Distribution Rate Daily distribution rate for calculation of pro rata distribution associated with proposed acquisition of CPPL. Distribution to Limited Partner, Minimum Quarterly Distribution, Per Unit Distribution to Limited Partner, Minimum Quarterly Distribution, Per Unit Distribution to Limited Partner, Minimum Quarterly Distribution, Per Unit Number of days in quarter Number of days in quarter Number of days in quarter used in calculation of pro-rated distribution to unitholders Limited Partners' Capital Account, Units Outstanding Limited Partners' Capital Account, Units Outstanding Termination Payment Termination Payment Termination payment due to terminable breach of the Merger Agreement Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments Equity Method Investments [Table Text Block] Document And Entity Information [Abstract] Document And Entity Information. Document Information [Table] Document Information [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Document Information, Document [Axis] Document Information, Document [Axis] Document [Domain] Document [Domain] Document Information [Line Items] Document Information [Line Items] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Units Outstanding Entity Common Stock, Shares Outstanding Related Party Transactions [Abstract] Schedule of Transactions With Affiliates Schedule of Related Party Transactions [Table Text Block] Schedule of Related Party Transactions, Long-Term Debt Schedule of Related Party Transactions, Long-Term Debt [Table Text Block] [Table Text Block] for Schedule of Related Party Transactions, Long-Term Debt [Table] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Predecessor Predecessor [Member] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Millennium Pipeline Millennium Pipeline [Member] Millennium Pipeline Company, L.L.C. Hardy Storage Hardy Storage [Member] Hardy Storage Company, LLC [Member] Pennant Pennant [Member] Pennant Midstream, L.L.C. [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Contributions to equity investees Distributions of earnings from equity investees Partners' Capital Account, Distributions Return of capital from equity investees Partners' Capital Account, Return of Capital Supplemental Cash Flow Information [Abstract] Additional Information Regarding Condensed Statements Of Consolidated Cash Flows Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Income Tax Disclosure [Abstract] Effective income tax rates Effective Income Tax Rate Reconciliation, Percent Federal statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Fair Value Disclosures [Abstract] Carrying Amount And Estimated Fair Values Of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] Long-term Debt Long-term Debt Long-term debt Long-term Debt and Capital Lease Obligations Long-term debt-affiliated, Estimated Fair Value Long-term Debt, Fair Value Other Nonoperating Income (Expense) [Abstract] Schedule Of Other, Net Schedule of Other Nonoperating Income (Expense) [Table Text Block] Risks and Uncertainties [Abstract] Schedule of Concentration Of Credit Risk Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Equity Method Investments [Abstract] Equity Method Investments [Abstract] Order [Axis] Order [Axis] Order [Axis] Order [Domain] Order [Domain] [Domain] for Order [Axis] Previous [Member] Previous [Member] Previous [Member] Equity Method Investment, Initial Ownership Percentage Equity Method Investment, Initial Ownership Percentage Equity Method Investment, Initial Ownership Percentage Equity Method Investment, Ownership Percentage Equity Method Investment, Ownership Percentage Cash Received from Buy-In Cash Received from Buy-In Cash Received from Buy-In Gain on Buy-In Gain on Buy-In Gain on Buy-In Goodwill and Intangible Assets Disclosure [Abstract] Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Supplemental Cash Flow Information Cash Flow, Supplemental Disclosures [Text Block] Regulatory Assets and Liabilities Disclosure [Abstract] Regulatory Matters Public Utilities Disclosure [Text Block] Gain On Sale of Assets [Abstract] Gain On Sale of Assets [Abstract] Gain On Sale Of Assets Property, Plant and Equipment Disclosure [Text Block] Noncontrolling Interest Noncontrolling Interest [Member] Net Income (Loss) Allocated to Limited Partners Net Income (Loss) Allocated to Limited Partners Noncontrolling Interest, Increase from Subsidiary Equity Issuance Noncontrolling Interest, Increase from Subsidiary Equity Issuance Change from net income attributable to the Partnership and transfers to noncontrolling interest Change from net income attributable to the Partnership and transfers to noncontrolling interest Change from net income attributable to the Partnership and transfers to noncontrolling interest Concentration Risk [Table] Concentration Risk [Table] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Concentration Risk [Line Items] Concentration Risk [Line Items] Concentration Risk, Benchmark Description Concentration Risk, Benchmark Description Schedule of Related Party Transactions, Long-Term Debt [Table] Schedule of Related Party Transactions, Long-Term Debt [Table] Schedule of Related Party Transactions, Long-Term Debt [Table] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] London Interbank Offered Rate (LIBOR) London Interbank Offered Rate (LIBOR) [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Notes Due 2020 Notes Due 2020 [Member] Notes Due 2020 [Member] Schedule of Related Party Transactions, Long-Term Debt [Line Items] Schedule of Related Party Transactions, Long-Term Debt [Line Items] [Line Items] for Schedule of Related Party Transactions, Long-Term Debt [Table] Debt Instrument, Issuance Date Debt Instrument, Issuance Date Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Maturity Date Debt Instrument, Maturity Date Concentration Risk Disclosure Concentration Risk Disclosure [Text Block] Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Assets Assets [Abstract] Current Assets Assets, Current [Abstract] Cash and cash equivalents Accounts receivable (less reserve of $0.3 and $0.3, respectively) Accounts Receivable, Net, Current Accounts receivable-affiliated Accounts Receivable, Related Parties, Current Materials and supplies, at average cost Inventory, Raw Materials and Supplies, Gross Exchange gas receivable Exchange gas receivable Exchange gas receivable. Deferred property taxes Deferred Property Taxes Deferred property taxes Prepayments and other Other Assets, Current Total Current Assets Assets, Current Investments Regulated Entity, Other Assets, Noncurrent [Abstract] Unconsolidated affiliates Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Other investments Other Long-term Investments Total Investments Investments and Other Noncurrent Assets Property, Plant and Equipment Public Utilities, Property, Plant and Equipment [Abstract] Property, plant and equipment Public Utilities, Property, Plant and Equipment, Plant in Service Accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Net Property, Plant and Equipment Public Utilities, Property, Plant and Equipment, Net Other Noncurrent Assets Assets, Noncurrent [Abstract] Regulatory assets Regulatory Assets, Noncurrent Goodwill Goodwill Postretirement and postemployment benefits assets Defined Benefit Plan, Assets for Plan Benefits, Noncurrent Deferred charges and other Deferred charges and other Deferred charges and other Total Other Noncurrent Assets Other Assets, Noncurrent Total Assets Assets Liabilities and Equity and Partners' Capital Liabilities and Equity [Abstract] Liabilities Liabilities [Abstract] Current Liabilities Liabilities, Current [Abstract] Short-term borrowings Short-term Debt Short-term borrowings-affiliated Short Term Borrowings Related Parties The amount for short term borrowings (written promise to pay), due to related parties. Accounts payable Accounts Payable, Current Accounts payable-affiliated Accounts Payable, Related Parties, Current Customer deposits Customer Deposits, Current Taxes accrued Taxes Payable, Current Exchange gas payable Exchange gas payable Exchange gas payable Deferred revenue Deferred Revenue, Current Accrued capital expenditures Accrued Capital Expenditures Accrued Capital Expenditures Accrued compensation and related costs Employee-related Liabilities, Current Other accruals Other Liabilities, Current Total Current Liabilities Liabilities, Current Noncurrent Liabilities Liabilities, Noncurrent [Abstract] Long-term debt-affiliated Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Accrued liability for postretirement and postemployment benefits Pension and Other Postretirement and Postemployment Benefit Plans, Liabilities, Noncurrent Regulatory liabilities Regulatory Liability, Noncurrent Asset retirement obligations Asset Retirement Obligations, Noncurrent Other noncurrent liabilities Other Liabilities, Noncurrent Total Noncurrent Liabilities Liabilities, Noncurrent Total Liabilities Liabilities Equity and Partners' Capital Partners' Capital [Abstract] Limited Partners' Capital Account Limited Partners' Capital Account Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total Columbia Pipeline Partners LP partners' equity and capital Partners' Capital Noncontrolling Interest in Columbia OpCo Partners' Capital Attributable to Noncontrolling Interest Total Equity and Partners' Capital Partners' Capital, Including Portion Attributable to Noncontrolling Interest Total Liabilities and Equity and Partners' Capital Liabilities and Equity Pension And Other Postretirement Benefits [Abstract] Pension And Other Postretirement Benefits [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Pension Plan Pension Plan [Member] Other Postretirement Benefits Other Postretirement Benefit Plan [Member] Defined Benefit Plan, Asset Categories [Axis] Defined Benefit Plan, Asset Categories [Axis] Plan Asset Categories [Domain] Plan Asset Categories [Domain] Industry Sector [Axis] Industry Sector [Axis] Industry Sector [Domain] Industry Sector [Domain] Equity Securities by Entity Size [Axis] Equity Securities by Entity Size [Axis] Equity Securities, Entity Size [Domain] Equity Securities, Entity Size [Domain] Equity Securities by Investment Objective [Axis] Equity Securities by Investment Objective [Axis] Equity Securities, Investment Objective [Domain] Equity Securities, Investment Objective [Domain] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan, Contributions by Employer Defined Benefit Plan, Contributions by Employer Change in Projected Benefit Obligation, Net of Plan Assets, Due to Interim Measurement Change in Projected Benefit Obligation, Net of Plan Assets, Due to Interim Measurement Change in Projected Benefit Obligation, net of plan assets, due to interim measurement - associated with July 1, 2016 remeasurement. Decrease in regulatory assets due to interim measurement Decrease in regulatory assets due to interim measurement Decrease in regulatory assets due to interim measurement as a result of the July 1, 2016 remeasurement. Change in Accumulated Other Comprehensive Income Due to Interim Measurement Change in Accumulated Other Comprehensive Income Due to Interim Measurement Change in Accumulated Other Comprehensive Income due to interim measurement - associated with the July 1, 2016 remeasurement Change in Net Periodic Benefit Cost due to Interim Measurement Change in Net Periodic Benefit Cost due to Interim Measurement Change in Net Periodic Benefit Cost due to Interim Measurement - associated with August 31, 2012 pension plan settlement Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments Increase in regulatory assets due to interim measurement Increase in regulatory assets due to interim measurement Increase in regulatory assets due to interim measurement as a result of the July 1, 2016 remeasurement. Decrease in regulatory liabilities due to interim measurement Decrease in regulatory liabilities due to interim measurement Decrease in regulatory liabilities due to interim measurement as a result of the July 1, 2016 remeasurement. Other Comprehensive Income (Loss), Tax [Abstract] Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Other, Net Other Income and Other Expense Disclosure [Text Block] Income Statement [Abstract] Parent Parent [Member] Operating Revenues Gross Profit [Abstract] Transportation revenues Natural Gas Midstream Revenue Transportation revenues-affiliated Natural Gas Midstream Revenue Related Party Midstream refers to those gas industry activities that fall between exploration and production (upstream) and refining and marketing (downstream). It may be applied to the gathering, processing, transmission and storage of natural gas; including the treating of natural gas to remove impurities, along with the sale of by-products such as residue gas, natural gas liquids and condensate with a related party. Storage revenues Natural Gas Storage Revenue Storage revenues-affiliated Natural Gas Storage Revenue Related Parties Revenue from storage facilities, such as a LNG ( Liquefied Natural Gas) storage facility. Other revenues Other Revenue, Net Total Operating Revenues Revenues Operating Expenses Operating Expenses [Abstract] Operation and maintenance Utilities Operating Expense, Maintenance and Operations Operation and maintenance-affiliated Utilities Operating Expense, Maintenance and Operations Related Parties Amount of operating expense for routine plant maintenance, repairs and operations of regulated operation. Gain on sale of assets Gain (Loss) on Disposition of Assets Property and other taxes Taxes, Miscellaneous Total Operating Expenses Operating Expenses Equity Earnings in Unconsolidated Affiliates Income (Loss) from Equity Method Investments Operating Income Operating Income (Loss) Other Income (Deductions) Interest expense Interest Expense Interest expense-affiliated Interest Expense, Related Party Other, net Other Nonoperating Income (Expense) Total Other Income (Deductions), net Nonoperating Income (Expense) Income before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income Taxes Income Tax Expense (Benefit) Income (Loss), Including Portion Attributable to Noncontrolling Interest Income (Loss) Attributable to Noncontrolling Interest Income (Loss) Attributable to Noncontrolling Interest Net Income (Loss) Allocated to Limited Partners Net income attributable to partners' ownership interest subsequent to IPO per limited partner unit (basic and diluted) Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax [Abstract] Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax Net Income (Loss), Per Outstanding Limited Partnership and General Partnership Unit, Basic and Diluted, Net of Tax Weighted average limited partner units outstanding (basic and diluted) Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract] Weighted Average Number of Shares Outstanding, Basic and Diluted Weighted Average Number of Shares Outstanding, Basic and Diluted Transactions With Affiliates Related Party Transactions Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Other Commitments and Contingencies [Table] Other Commitments and Contingencies [Table] Other Commitments and Contingencies [Table] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Guarantee of Indebtedness of Others Guarantee of Indebtedness of Others [Member] Letters of Credit Letter of Credit [Member] Other Commitments and Contingencies [Line Items] Other Commitments and Contingencies [Line Items] [Line Items] for Other Commitments and Contingencies [Table] 2016 Guarantee Obligations Maximum Exposure Year One Guarantee obligations maximum exposure year one. 2017 Guarantee Obligations Maximum Exposure Year Two Guarantee obligations maximum exposure year two. 2018 Guarantee Obligations Maximum Exposure Year Three Guarantee obligations maximum exposure year three. 2019 Guarantee Obligations Maximum Exposure Year Four Guarantee obligations maximum exposure year four. 2020 Guarantee Obligations Maximum Exposure Year Five Guarantee obligations maximum exposure year five. After Guarantee Obligations Maximum Exposure Thereafter Guarantee obligations maximum exposure thereafter. Total Guarantor Obligations, Maximum Exposure, Undiscounted Accumulated Other Comprehensive Loss [Table] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest [Member] AOCI Attributable to Noncontrolling Interest AOCI Attributable to Noncontrolling Interest [Member] Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Beginning Balance Predecessor net tax liabilities not assumed by Columbia OpCo Partners Capital Predecessor Net Liabilities Not Assumed By Subsidiary Partners Capital Predecessor Net Liabilities Not Assumed By Subsidiary Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Other Comprehensive Income (Loss) Other Comprehensive Income (Loss), Net of Tax Ending Balance Equity [Abstract] Initial Public Offering Stockholders' Equity Note Disclosure [Text Block] Net Income Per Limited Partner Unit [Abstract] Net Income Per Limited Partner Unit [Abstract] Schedule Of Earnings Per Unit [Table] Schedule Of Earnings Per Unit [Table] Schedule Of Earnings Per Unit [Table] Minimum Minimum [Member] Timing [Axis] Timing [Axis] Timing [Axis] Timing [Domain] Timing [Domain] [Domain] for Timing [Axis] Annualized Annualized [Member] Annualized [Member] Schedule Of Earnings Per Unit [Line Items] Schedule Of Earnings Per Unit [Line Items] [Line Items] for Schedule Of Earnings Per Unit [Table] Distribution Made to Limited Partner, Distributions Paid, Per Unit Distribution Made to Limited Partner, Distributions Paid, Per Unit Goodwill Supplemental Cashflow [Table] supplemental cashflow [Table] supplemental cashflow [Table] Supplemental Cashflow [Axis] Supplemental Cashflow [Axis] Supplemental Cashflow [Axis] Supplemental Cash Flow [Line Items] Supplemental Cash Flow [Line Items] Supplemental Cash Flow [Line Items] Capital expenditures included in current liabilities Capital Expenditures Incurred but Not yet Paid Cash paid for interest, net of interest capitalized amounts Interest Paid, Net Other Ownership Interests Name [Axis] Other Ownership Interests Name [Axis] Other Ownership Interests, Name [Domain] Other Ownership Interests, Name [Domain] Incentive Distribution Rights [Member] Incentive Distribution Rights [Member] Incentive Distribution Rights Distribution Made to Limited Partner, Cash Distributions Declared Distribution Made to Limited Partner, Cash Distributions Declared Incentive Distribution, Distribution Incentive Distribution, Distribution Partners' Capital Account, Distributions Cash Distributions Declared Total distributions to each interest (i.e., general partner, limited partners and incentive distribution rights). Undistributed Earnings, Basic Undistributed Earnings, Basic Expected Modernization Investment Expected Modernization Investment Expected Modernization Investment Modernization Program Recovery Modernization Program Recovery Modernization Program Recovery Annual Capital Cost Recovery Mechanism Extension Limit Annual Capital Cost Recovery Mechanism Extension Limit Annual Capital Cost Recovery Mechanism Extension Limit Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] TransCanada PipeLine USA Ltd. TransCanada PipeLine USA Ltd. [Member] TransCanada PipeLine USA Ltd. Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type Short-term Debt, Type [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Money Pool Money Pool [Member] Money Pool [Member] Revolving Credit Facility Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Transportation and Storage Services Transportation and Storage Services [Member] Transportation and Storage Services [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Merger Related Utilities Operating Expense Maintenance and Operations Related Parties Merger Related Utilities Operating Expense Maintenance and Operations Related Parties Amount of operating expense for routine plant maintenance, repairs and operations of regulated operation related to the Merger. Interest Expense, Long-term Debt Interest Expense, Long-term Debt Allowance for Funds Used During Construction, Capitalized Interest Allowance for Funds Used During Construction, Capitalized Interest Short-term Debt, Weighted Average Interest Rate Short-term Debt, Weighted Average Interest Rate Interest Expense, Short-term Borrowings Interest Expense, Short-term Borrowings Accounts receivable Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Debt Instrument, Basis Spread on Variable Rate Debt Instrument, Basis Spread on Variable Rate Distribution to Parent Distribution to Parent Distribution to Parent Components Of Accumulated Other Comprehensive Loss Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] AFUDC Equity Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Miscellaneous Other Nonoperating Income Total Other, net Short-term Debt [Abstract] Short-Term Borrowings Short-term Debt [Text Block] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Asset Retirement Obligation [Abstract] Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Beginning Balance Noncontributed net parent investment adjustments Noncontributed net parent investment adjustments Noncontributed net parent investment adjustments Accretion expense Asset Retirement Obligation, Accretion Expense Additions Asset Retirement Obligation, Liabilities Incurred Settlements Asset Retirement Obligation, Liabilities Settled Change in estimated cash flows Asset Retirement Obligation, Revision of Estimate Ending Balance Change From Net Income Attributable to the Partnership and Transfers to Noncontrolling Interest Change From Net Income Attributable to the Partnership and Transfers to Noncontrolling Interest [Table Text Block] Change From Net Income Attributable to the Partnership and Transfers to Noncontrolling Interest Fair Value Fair Value Disclosures [Text Block] Changes In Company's Liability For Asset Retirement Obligations Schedule of Change in Asset Retirement Obligation [Table Text Block] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Credit Concentration Risk Credit Concentration Risk [Member] Revenues Concentration Risk, Percentage Concentration Risk, Percentage Pension and Other Postretirement Benefit Expense [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Service Cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Expected return on assets Defined Benefit Plan, Expected Return on Plan Assets Amortization of prior service (credit) cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Recognized actuarial loss Defined Benefit Plan, Amortization of Gains (Losses) Total Net Periodic Benefits Cost Defined Benefit Plan, Net Periodic Benefit Cost Defined Benefit Plan Net Periodic Benefit Costs Defined Benefit Plan Net Periodic Benefit Costs Defined Benefit Plan Net Periodic Benefit Cost Equity Method Investments Equity Method Investments and Joint Ventures Disclosure [Text Block] Subsequent Event Subsequent Events [Text Block] Pension And Other Postretirement Benefits Pension and Other Postretirement Benefits Disclosure [Text Block] Statement of Partners' Capital [Abstract] Equity Method Investment, Percent Not Contributed to Partnership Equity Method Investment, Percent Not Contributed to Partnership Equity Method Investment, Percent Not Contributed to Partnership Statement of Comprehensive Income [Abstract] Net unrealized gain on cash flow hedges Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Total other comprehensive income Other Comprehensive Income, Net of Tax and Transaction Adjustments Other Comprehensive Income, Net of Tax and Transaction Adjustments Total comprehensive income subsequent to IPO Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Less: Comprehensive income attributable to noncontrolling interest subsequent to IPO Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Comprehensive income attributable to limited partners subsequent to IPO Comprehensive Income (Loss), Net of Tax, Attributable to Limited Partners Comprehensive Income (Loss), Net of Tax, Attributable to Limited Partners Schedule Of Net Income Per Limited Partner Unit Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Accumulated Other Comprehensive Loss [Line Items] Unrealized loss, amortization period Unrealized Gain Loss On Derivatives, Amortization Period Unrealized Gain Loss On Derivatives, Amortization Period Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Before Tax Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Before Tax Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Before Tax Asset Retirement Obligations Asset Retirement Obligation Disclosure [Text Block] Schedule of Guarantee Obligations Schedule of Guarantor Obligations [Table Text Block] Statement of Stockholders' Equity [Abstract] Beginning Balance Contributed/Noncontributed Net Parent Investment Adjustments Contributed/Noncontributed Net Parent Investment Adjustments Contributed/Noncontributed Net Parent Investment Adjustments Allocation of Net Investment to Unitholders Allocation of Net Investment to Unitholders Allocation of Net Investment to Unitholders Allocation of Accumulated Other Comprehensive Loss to Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Purchase of additional interest in Columbia OpCo Distributions to the noncontrolling interest in Columbia OpCo Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Quarterly distributions to unitholders Limited Partners' Capital Account, Distribution Amount Transfers From Parent Net Transfers (To) From Parent Net Transfers (To) From Parent Ending Balance Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax Net Income Per Limited Partner Unit Earnings Per Share [Text Block] Income Taxes Income Tax Disclosure [Text Block] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Recent Accounting Pronouncements Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Transportation revenues Storage revenues Other revenues Related Party Transaction, Other Revenues from Transactions with Related Party Operation and maintenance Interest expense Interest income Interest Income, Related Party Short-term borrowings Accounts payable Accounts receivable less reserve Allowance for Doubtful Accounts Receivable, Current Limited Partners' Capital Account, Units Issued Limited Partners' Capital Account, Units Issued Gain on Conveyances Gain on Conveyances Amount of gain (loss) on conveyances Gain on Conveyances Cash Received Gain on Conveyances Cash Received Gain on Conveyances Cash Received Deferred Gains On Conveyances Deferred Gains On Conveyances Deferred Gains (Losses) On Conveyances Schedule of Guarantor Obligations [Table] Purchase Commitment, Excluding Long-term Commitment [Table] Commercial Paper Commercial Paper [Member] Other Commitments And Contingencies [Line Items] Purchase Commitment, Excluding Long-term Commitment [Line Items] Guarantees Line of Credit Facility, Maximum Borrowing Capacity Commercial Paper Commercial Paper Credit facilities borrowings Long-term Line of Credit Letters of Credit Outstanding, Amount Letters of Credit Outstanding, Amount Ozone Level Maximum Ozone Level Maximum Ozone Level Maximum Dwellings within the potential impact area Dwellings within the potential impact area Dwellings within the potential impact area Gathering line nominal design inches Gathering line nominal design inches Gathering line nominal design inches Feet under the surface water Feet under the surface water Feet under the surface water Significant Assumptions [Abstract] Significant Assumptions [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Short-term Debt [Line Items] Short-term Debt [Line Items] Line of Credit Facility, Amount Outstanding Accelerated amortization of deferred costs Accelerated amortization of deferred costs Accelerated amortization of deferred costs Components Of The Plans' Net Periodic Benefits Cost Schedule of Net Benefit Costs [Table Text Block] Schedule of Assumptions Used Schedule of Assumptions Used [Table Text Block] Basis of Accounting Presentation Basis of Accounting [Text Block]