Commitments and Contingencies Disclosure [Abstract] Other Commitments and Contingencies [Table] Other Commitments and Contingencies [Table] Other Commitments and Contingencies [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Line of Credit [Member] Line of Credit [Member] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Guarantee of Indebtedness of Others [Member] Guarantee of Indebtedness of Others [Member] Other Commitments and Contingencies [Line Items] Other Commitments and Contingencies [Line Items] [Line Items] for Other Commitments and Contingencies [Table] Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted Long-term Line of Credit Guarantee Obligations Maximum Exposure Year One Guarantee Obligations Maximum Exposure Year One Guarantee obligations maximum exposure year one. Guarantee Obligations Maximum Exposure Year Two Guarantee Obligations Maximum Exposure Year Two Guarantee obligations maximum exposure year two. Guarantee Obligations Maximum Exposure Year Three Guarantee Obligations Maximum Exposure Year Three Guarantee obligations maximum exposure year three. Guarantee Obligations Maximum Exposure Year Four Guarantee Obligations Maximum Exposure Year Four Guarantee obligations maximum exposure year four. Guarantee Obligations Maximum Exposure Year Five Guarantee Obligations Maximum Exposure Year Five Guarantee obligations maximum exposure year five. Guarantee Obligations Maximum Exposure Thereafter Guarantee Obligations Maximum Exposure Thereafter Guarantee obligations maximum exposure thereafter. Asset Retirement Obligation [Abstract] Changes In Company's Liability For Asset Retirement Obligations Schedule of Change in Asset Retirement Obligation [Table Text Block] Net Income Per Limited Partner Unit [Abstract] Net Income Per Limited Partner Unit [Abstract] Schedule of Undistributed Net Income Schedule of Undistributed Net Income [Table Text Block] [Table Text Block] for Schedule of Undistributed Net Income [Table] Schedule Of Net Income Per Limited Partner Unit Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Other Comprehensive Income (Loss), Tax [Abstract] Accumulated Other Comprehensive Loss [Table] Accumulated Other Comprehensive Income (Loss) [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Predecessor [Member] Predecessor [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Millennium Pipeline Millennium Pipeline [Member] Millennium Pipeline Company, L.L.C. Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Beginning Balance Accumulated Other Comprehensive Income (Loss), Net of Tax 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), Net of Tax Other Comprehensive Income (Loss), Net of Tax Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest Allocation of Accumulated Other Comprehensive Loss To Noncontrolling Interest Ending Balance Goodwill and Intangible Assets Disclosure [Abstract] Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value Fair Value Disclosures [Text Block] Statement of Cash Flows [Abstract] Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] 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 401(k) profit sharing contribution Share-based Compensation Gain on sale of assets Gain (Loss) on Disposition of Property Plant Equipment Income from unconsolidated affiliates Income from Unconsolidated Affiliates Income from unconsolidated affiliates. Amortization of Financing Costs Amortization of Financing 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 Accruals Increase decrease in other accruals. 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 Distributions from (contributions to) equity investees Payments to Acquire Equity Method Investments 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 Issuance of long-term debt-affiliated Proceeds from Issuance of Long-term Debt Payments of long-term debt-affiliated, including current portion Repayments of Long-term Debt 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 Partners' Capital Account, Distributions Partners' Capital Account, Distributions Net Cash Flows from Financing Activities Net Cash Provided by (Used in) Financing Activities Change in cash and cash equivalents Change in cash and cash equivalents from continuing operations Change in cash and cash equivalents from continuing operations. Cash and cash equivalents at beginning of period Cash and Cash Equivalents, at Carrying Value Cash and Cash Equivalents at End of Period Other Income and Expenses [Abstract] Other, Net Other Income and Other Expense Disclosure [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] Common Units [Member] Common Units [Member] Common Units [Member] Subordinated Units [Member] Subordinated Units [Member] Subordinated Units [Member] 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 Equity [Abstract] 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 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] Equity Method Investments [Abstract] Equity Method Investments [Abstract] Equity Method Investments Equity Method Investments and Joint Ventures Disclosure [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] Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax Debt Instrument, Maturity Date Debt Instrument, Maturity Date Income Statement [Abstract] 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] 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) Other Nonoperating Income (Expense) [Abstract] Interest expense-affiliated Interest Expense Other, net Other Nonoperating Income (Expense) Total Other Deductions, net Nonoperating Income (Expense) Income before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Income Taxes Income Tax Expense (Benefit) Net Income Income (Loss) Attributable to Noncontrolling Interest Income (Loss) Attributable to Noncontrolling Interest Net Income (Loss) Allocated to Limited Partners 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 Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Asset Retirement Obligations Asset Retirement Obligation Disclosure [Text Block] Components Of Accumulated Other Comprehensive Loss Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Related Party Transactions [Abstract] Transactions With Affiliates Related Party Transactions Disclosure [Text Block] Purchase Commitment, Excluding Long-term Commitment [Table] Purchase Commitment, Excluding Long-term Commitment [Table] Revolving Credit Facility [Member] Revolving Credit Facility [Member] Letter of Credit Letter of Credit [Member] Purchase Commitment, Excluding Long-term Commitment [Axis] Purchase Commitment, Excluding Long-term Commitment [Axis] Purchase Commitment, Excluding Long-term Commitment [Domain] Purchase Commitment, Excluding Long-term Commitment [Domain] Purchase Commitment, Excluding Long-term Commitment [Line Items] Purchase Commitment, Excluding Long-term Commitment [Line Items] Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Guarantee Obligations Maximum Exposure Year One Letters of Credit Outstanding, Amount 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] Current portion of long-term debt Long-term Debt and Capital Lease Obligations, Current Current Portion of Long Term Debt, Fair Value Current Portion of Long Term Debt, Fair Value The fair value amount of the current portion of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. Long-term debt, Carrying Amount Long-term Debt, Gross Long-term debt, Estimated Fair Value Long-term Debt, Fair Value 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 2015 Notes Due 2015 [Member] Notes Due 2015 [Member] Notes Due 2016 Notes Due 2016 [Member] Notes Due 2016 Notes Due 2025 Notes Due 2025 [Member] Notes Due 2025 Notes Due 2032 Notes Due 2032 [Member] Notes Due 2032 [Member] Notes Due 2037 Notes Due 2037 [Member] Notes Due 2037 Notes Due 2037 [1] Notes Due 2037 [1] [Member] Notes Due 2037 [1] Notes Due 2042 Notes Due 2042 [Member] Notes Due 2042 [Member] Notes Due 2042 [1] Notes Due 2042 [1] [Member] Notes Due 2042 Notes Due 2016 [1] Notes Due 2016 [1] [Member] Notes Due 2016 [1] 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 Long-term Debt Long-term Debt Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Earnings Per Share [Abstract] Schedule of Undistributed Net Income [Table] Schedule of Undistributed Net Income [Table] Schedule of Undistributed Net Income [Table] Schedule of Undistributed Net Income [Line Items] Schedule of Undistributed Net Income [Line Items] [Line Items] for Schedule of Undistributed Net Income [Table] Net Income (Loss) Allocated to Limited Partners Distribution Made to Limited Partner, Cash Distributions Declared Distribution Made to Limited Partner, Cash Distributions Declared Incentive Distribution, Distribution Incentive Distribution, Distribution Undistributed Earnings, Basic Undistributed Earnings, Basic Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Hardy Storage [Member] Hardy Storage [Member] Hardy Storage Company, LLC [Member] Pennant [Member] Pennant [Member] Pennant Midstream, L.L.C. [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Contributions Partners' Capital Account, Contributions Distributions Limited Partners' Capital Account, Distribution Amount Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital Schedule Of Other, Net [Table] Schedule Of Other, Net [Table] Schedule Of Other, Net [Table] Schedule Of Other, Net [Line Items] Schedule Of Other, Net [Line Items] [Line Items] for Schedule Of Other, Net [Table] AFUDC Equity Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Miscellaneous Other Nonoperating Income Total Other, net Statement of Stockholders' Equity [Abstract] Noncontrolling Interest [Member] Noncontrolling Interest [Member] Parent [Member] Parent [Member] Partner Type [Axis] Partner Type [Axis] Partner Type of Partners' Capital Account, Name [Domain] Partner Type of Partners' Capital Account, Name [Domain] Limited Partner [Member] Limited Partner [Member] Beginning Balance Partners' Capital, Including Portion Attributable to Noncontrolling Interest Contribution of capital from parent 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 Net proceeds from IPO Partners' Capital Account, Public Sale of Units Net of Offering Costs Purchase of additional interest in Columbia OpCo Noncontrolling Interest, Increase from Subsidiary Equity Issuance Distribution to the noncontrolling interest in Columbia OpCo Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Limited Partners' Capital Account, Distribution Amount Transfers from parent Net Transfers (To) From Parent Net Transfers (To) From Parent Ending Balance Changes in Company's Liability for Asset Retirement Obligations [Table] Changes in Company's Liability for Asset Retirement Obligations [Table] Changes in Company's Liability for Asset Retirement Obligations [Table] Asset Retirement Obligation [Axis] Asset Retirement Obligation [Axis] Asset Retirement Obligation [Axis] Beginning Balance Asset Retirement Obligations, Noncurrent 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 Risks and Uncertainties [Abstract] Concentration Risk Disclosure Concentration Risk Disclosure [Text Block] Supplemental Cash Flow Information [Abstract] 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 Cash paid for income taxes Income Taxes Paid Pension and Other Postretirement Benefit Expense [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plans Disclosures, Defined Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Pension Plan [Member] Pension Plan [Member] Other Postretirement Benefits [Member] Other Postretirement Benefit Plan [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Employer contributions Defined Benefit Plan, Contributions by Employer Regulatory Assets and Liabilities Disclosure [Abstract] Regulatory Matters Public Utilities Disclosure [Text Block] 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, Net of Tax and Transaction Adjustments Other Comprehensive Income, Net of Tax and Transaction Adjustments Other Comprehensive Income, Net of Tax and Transaction Adjustments Total other comprehensive income 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 Short-term Debt [Abstract] Short-Term Borrowings Short-term Debt [Text Block] Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Federal Funds Effective Swap Rate Federal Funds Effective Swap Rate [Member] Eurodollar Eurodollar [Member] Test Period [Axis] Test Period [Axis] Test Period [Axis] Test Period [Domain] Test Period [Domain] [Domain] for Test Period [Axis] Period 1 Period 1 [Member] Period 1 [Member] Period 2 Period 2 [Member] Period 2 [Member] Period 3 Period 3 [Member] Period 3 [Member] Acquisition Period Acquisition Period [Member] Acquisition Period [Member] Revolving Credit Facility Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Short-term Debt [Line Items] Short-term Debt [Line Items] Revolving credit facility Basis Spread on Variable Rate Debt Instrument, Basis Spread on Variable Rate Margin Rate Margin Rate Margin Rate Line of Credit Facility, Commitment Fee Percentage Line of Credit Facility, Commitment Fee Percentage Default Provision Floor Default Provision Floor Default Provision Floor Ratio of Indebtedness to Net Capital Ratio of Indebtedness to Net Capital Letters of Credit Outstanding Statement of Financial Position [Abstract] 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. Regulatory assets Regulatory Assets, Current Deferred property taxes Deferred Property Taxes Deferred property taxes Deferred income taxes Deferred Tax Assets, Net, Current 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] Current portion of long-term debt-affiliated 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 Regulatory liabilities Regulatory Liability, Current Legal and environmental Legal and environmental reserves Legal and environmental reserves. Accrued capital expenditures Accrued Capital Expenditures Accrued Capital Expenditures Other accruals Other Liabilities, Current Total Current Liabilities Liabilities, Current Noncurrent Liabilities Liabilities, Noncurrent [Abstract] Long-term debt-affiliated Long-term Debt and Capital Lease Obligations 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 Other noncurrent liabilities Other Liabilities, Noncurrent Total Noncurrent Liabilities Liabilities, Noncurrent Total Liabilities Liabilities Equity and Partners' Capital Partners' Capital [Abstract] Net parent investment Other Partners' Capital Accumulated other comprehensive loss Limited Partners' Capital Account Limited Partners' Capital Account 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 Total Liabilities and Equity and Partners' Capital Liabilities and Equity Supplemental Cash Flow Information Cash Flow, Supplemental Disclosures [Text Block] Pension And Other Postretirement Benefits Pension and Other Postretirement Benefits Disclosure [Text Block] Goodwill [Abstract] Goodwill [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Goodwill [Line Items] Goodwill [Line Items] Goodwill Transactions With Affiliates [Abstract] Transactions With Affiliates [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Storage revenues Other revenues Related Party Transaction, Other Revenues from Transactions with Related Party Interest expense Interest Expense, Related Party Interest income Interest Income, Related Party Accounts receivable Short-term Debt Accounts payable Long-term debt Schedule of Guarantee Obligations Contractual Obligation, Fiscal Year Maturity Schedule [Table 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] Components Of The Plans' Net Periodic Benefits Cost Schedule of Net Benefit Costs [Table Text Block] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Axis] 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 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 Pension Plans and Defined Benefit Postretirement Plans Disclosure [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 [Domain] 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] Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Additional Information Regarding Condensed Statements Of Consolidated Cash Flows Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Concentration Risk [Table] Concentration Risk [Table] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Credit Concentration Risk Credit Concentration Risk [Member] Concentration Risk [Line Items] Concentration Risk [Line Items] Revenues Concentration Risk, Percentage Concentration Risk, Percentage Schedule of Concentration Of Credit Risk Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Basis of Accounting Presentation [Abstract] Basis of Accounting Presentation [Abstract] Basis Of Accounting Presentation [Table] Basis Of Accounting Presentation [Table] Basis Of Accounting Presentation [Table] Corporate Joint Venture [Member] Corporate Joint Venture [Member] Basis Of Accounting Presentation [Line Items] Basis Of Accounting Presentation [Line Items] Basis Of Accounting Presentation [Line Items] Number Of Customers Number Of Customers Number of customers 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 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 Limited Liability Company or Limited Partnership, Managing Member or General Partner, Name Limited Liability Company or Limited Partnership, Managing Member or General Partner, Name Initial Public Offering [Abstract] Initial Public Offering [Abstract] Initial Public Offering [Table] Initial Public Offering [Table] Initial Public Offering [Table] Initial Public Offering [Line Items] Initial Public Offering [Line Items] [Line Items] for Initial Public Offering [Table] 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 Gain on Conveyances Gain on Conveyances Amount of gain (loss) on conveyances Deferred Gains On Conveyances Deferred Gains On Conveyances Deferred Gains (Losses) On Conveyances Effect On Tax Rate Due To Legislations [Table] Effect On Tax Rate Due To Legislations [Table] Effect On Tax Rate Due To Legislations [Table] Scenario [Axis] Income Taxes [Line Items] Income Taxes [Line Items] Income Taxes [Line Items] Effective income tax rates Effective Income Tax Rate Reconciliation, Percent Corporate Income Tax Rate Corporate Income Tax Rate Corporate Income Tax Rate Concentration Risk, Benchmark Description Concentration Risk, Benchmark Description 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] Money Pool Money Pool [Member] Money Pool [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Columbia OpCo Columbia OpCo [Member] Columbia OpCo [Member] Transportation and Storage Services Transportation and Storage Services [Member] Transportation and Storage Services [Member] 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 Reimbursement of Preformation Capital Reimbursement of Preformation Capital Reimbursement of Preformation Capital Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] 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 Share Distribution, Date Share Distribution, Date Share Distribution, Date Common Stock, Shares Authorized Common Stock, Shares Authorized Common Stock, Shares, Issued Common Stock, Shares, Issued Distribution Payable Shareholder Date of Record Distribution Payable Shareholder Date of Record Date the holder must own the stock to be entitled to the distribution, in CCYY-MM-DD format. Stock Trade Date Stock Trade Date Initial date that the security began trading "regular way" Acres Conveyed Acres Conveyed Acres Conveyed Schedule Of Earnings Per Unit [Table] Schedule Of Earnings Per Unit [Table] Schedule Of Earnings Per Unit [Table] 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 Columbia Energy Group Columbia Energy Group [Member] Columbia Energy Group Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] Over-Allotment Option [Member] Over-Allotment Option [Member] 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 Shares Issued, Price Per Share Shares Issued, Price Per Share Underwriting discounts, structuring fees, and offering expenses Payments of Stock Issuance Costs Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis of Accounting Presentation Basis of Accounting [Text Block] Schedule Of Other, Net [Table Text Block] Schedule Of Other, Net [Table Text Block] [Table Text Block] for Schedule Of Other, Net [Table] Carrying Amount And Estimated Fair Values Of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Subsequent Events Subsequent Events [Text Block] Accounts receivable less reserve Allowance for Doubtful Accounts Receivable, Current Limited Partners' Capital Account, Units Issued Limited Partners' Capital Account, Units Issued Limited Partners' Capital Account, Units Outstanding Limited Partners' Capital Account, Units Outstanding Net Income Per Limited Partner Unit Earnings Per Share [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 Equity Method Investment, Ownership Percentage Equity Method Investment, Ownership Percentage 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 Expected Modernization Investment Expected Modernization Investment Expected Modernization Investment Modernization Program Recovery Modernization Program Recovery Modernization Program Recovery 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 Partners' Capital Account, Distributions Cash Distributions Declared Total distributions to each interest (i.e., general partner, limited partners and incentive distribution rights). Initial Public Offering Stockholders' Equity Note Disclosure [Text Block]