Accounting Policies [Abstract] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Significant accounting policies of the reporting entity. Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Line items for Significant accounting policies of the reporting entity. Number of natural gas distribution services customers Number of natural gas distribution services customers Number of customers the natural gas distribution service segment services. Segment Reporting, Disclosure of Major Customers Segment Reporting, Disclosure of Major Customers Long-term Debt, Unclassified [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Note Payable Due 2019 [Member] Note Payable Due 2019 [Member] Note Payable Due 2019 [Member] Note Payable Due 2024 [Member] Note Payable Due 2024 [Member] Note Payable Due 2024 [Member] Notes Payable Due 2044 [Member] Notes Payable Due 2044 [Member] A written promise to pay a note. Debt Instrument [Line Items] Debt Instrument [Line Items] Debt Instrument, Covenant Description Debt Instrument, Covenant Description Long-term Debt, Gross Long-term Debt, Gross Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Income Tax Disclosure [Abstract] Statement [Table] Statement [Table] Regulatory Liability [Axis] Regulatory Liability [Axis] Regulatory Liability [Domain] Regulatory Liability [Domain] Federal income tax rate changes [Member] Federal income tax rate changes [Member] Deferred income taxes deferred as a regulatory liability due to the enacted decrease in the Federal income tax rate. Statement [Line Items] Statement [Line Items] Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent NOL Limitation NOL Limitation Limitation on the utilization of NOLs arising after December 31, 2017, as a percent of taxable income with an indefinite carryforward, due to the enacted tax law. Regulatory Liability, Noncurrent Regulatory Liability, Noncurrent Regulatory Liability, Current Regulatory Liability, Current Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract] Employee Benefit Plans [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement 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] ONE Gas Pension Plans [Member] Pension Plan [Member] ONE Gas Postretirement Benefit Plans [Member] Other Postretirement Benefit Plan [Member] Employee Benefit Plans [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Components of net periodic benefit cost: Components of net periodic benefit cost: [Abstract] Components of net periodic benefit cost: [Abstract] 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 unrecognized prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Amortization of net loss Defined Benefit Plan, Amortization of Gains (Losses) Net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost OTHER INCOME AND OTHER EXPENSE [Abstract] OTHER INCOME AND OTHER EXPENSE [Abstract] Other Income and Other Expense Disclosure Other Income and Other Expense Disclosure [Text Block] Income Statement [Abstract] Gross Margin Gross Profit [Abstract] Revenues from contracts with customers Regulated Operating Revenue, Gas Other revenue Regulated Operating Revenue, Other Regulated Operating Revenue Regulated Operating Revenue Cost of natural gas Utilities Operating Expense, Gas and Petroleum Purchased Net margin Gross Profit Operating expenses Operating Expenses [Abstract] Operations and maintenance Utilities Operating Expense, Maintenance and Operations Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization General taxes Utilities Operating Expense, Taxes Total operating expenses Utilities Operating Expense Operating income Operating Income (Loss) Other expense, net Other Nonoperating Income (Expense) Interest expense, net Interest Expense Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income taxes Income Tax Expense (Benefit) Net income Net Income (Loss) Attributable to Parent Earnings per share Earnings Per Share [Abstract] Basic Earnings Per Share, Basic Diluted Earnings Per Share, Diluted Average shares (thousands) Average shares [Abstract] Average shares used in the EPS calculation. Basic Weighted Average Number of Shares Outstanding, Basic Diluted Weighted Average Number of Shares Outstanding, Diluted Dividends declared per share of stock Common Stock, Dividends, Per Share, Cash Paid STATEMENTS OF COMPREHENSIVE INCOME Parenthetical [Abstract] STATEMENTS OF COMPREHENSIVE INCOME Parenthetical [Abstract] Pension and other postemployment benefit plans, tax Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax Equity [Abstract] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Common Stock, Dividends, Per Share, Declared Common Stock, Dividends, Per Share, Declared Common Stock, Dividends, Declared, Annualized Basis Common Stock, Dividends, Declared, Annualized Basis Dividends declared during the period for each share of common stock outstanding, on an annualized basis. EARNINGS PER SHARE [Table] EARNINGS PER SHARE OF COMMON STOCK, BASIC AND DILUTED [Table] Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations. EARNINGS PER SHARE [Line Items] EARNINGS PER SHARE OF COMMON STOCK, BASIC AND DILUTED [Line Items] [Line Items] for Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations. Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Segments Segment Reporting, Policy [Policy Text Block] Recently Issued Accounting Standards Update New Accounting Pronouncements, Policy [Policy Text Block] Statement of Cash Flows [Abstract] Document Fiscal Year Focus Document Fiscal Year Focus Operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Deferred income taxes Deferred Income Tax Expense (Benefit) Share-based compensation expense Share-based Compensation Provision for doubtful accounts Provision for Doubtful Accounts Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Receivables Materials and supplies Increase (Decrease) in Materials and Supplies Natural gas in storage Increase (Decrease) in Inventories Asset removal costs Payments for Removal Costs Accounts payable Increase (Decrease) in Accounts Payable Accrued interest Increase (Decrease) in Interest Payable, Net Accrued taxes other than income Increase (Decrease) in Property and Other Taxes Payable Accrued liabilities Increase (Decrease) in Accrued Liabilities Customer deposits Increase (Decrease) in Customer Deposits Regulatory assets and liabilities Increase (Decrease) in Regulatory Assets and Liabilities Other assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Capital expenditures Payments to Acquire Property, Plant, and Equipment Other Payments for (Proceeds from) Other Investing Activities Cash used in investing activities Net Cash Provided by (Used in) Investing Activities Financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Repayments of notes payable, net Proceeds from (Repayments of) Commercial Paper Repurchase of common stock Payments for Repurchase of Common Stock Dividends paid Payments of Dividends Tax withholdings related to net share settlements of stock compensation Excess Tax Benefit from Share-based Compensation, Financing Activities Cash used in 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 Other Income and Other Expense Disclosure [Text Block] Other Nonoperating Income and Expense [Text Block] Document and Entity Information [Abstract] 4eba46a2-97a9-0056-c25c-d1cfa3a911f6 Document Information [Table] Document Information [Table] Document Information, Document [Axis] Document Information, Document [Axis] Document [Domain] Document [Domain] Document Information [Line Items] Document Information [Line Items] 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 Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Period Focus Document Fiscal Period Focus Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Statement of Financial Position [Abstract] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common stock, par value per share Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Common Stock, Shares, Outstanding Treasury stock, shares Treasury Stock, Shares Debt issuance costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net CREDIT FACILITIES [Abstract] CREDIT FACILITIES [Abstract] Line of Credit Facility [Table] Line of Credit Facility [Table] Lender Name [Axis] Lender Name [Axis] Line of Credit Facility, Lender [Domain] Line of Credit Facility, Lender [Domain] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Short-term Debt [Line Items] Line of Credit Facility [Line Items] Short-term Debt [Text Block] Short-term Debt [Text Block] Earnings Per Share [Text Block] Earnings Per Share [Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Class of Stock [Line Items] Class of Stock [Line Items] Stockholders' Equity Note Disclosure [Text Block] Stockholders' Equity Note Disclosure [Text Block] Derivatives and Fair Value Measurement [Abstract] Derivatives and Fair Value Measurement [Abstract] Derivatives Derivatives, Reporting of Derivative Activity [Policy Text Block] Fair Value Measurement Fair Value Measurement, Policy [Policy Text Block] DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS [Abstract] DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Disclosures Fair Value Disclosures [Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies [Table] Commitments and Contingencies [Table] Disclosure of commitments and contingencies [Table] Commitments and Contingencies [Line Items] Commitments and Contingencies [Line Items] [Line Items] for Disclosure of commitments and contingencies [Table] COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) [Abstract] ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) [Abstract] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Income Tax Disclosure Income Tax Disclosure [Text Block] Schedule of Net Benefit Costs [Table Text Block] Schedule of Net Benefit Costs [Table Text Block] Regulatory Assets and Liabilities [Abstract] Regulatory Assets and Liabilities [Abstract] SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Table] SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Table] Tabular disclosure of assets and liabilities that result from rate actions of a regulator. Regulatory assets are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability. Regulatory Assets and Liabilities [Axis] Regulatory Assets and Liabilities [Axis] Information by type of regulatory asset/liabilities itemized in a table of regulatory assets/liabilities. Regulatory Assets and Liabilities [Domain] Regulatory Assets and Liabilities [Domain] [Domain] for Information by type of regulatory asset/liabilities itemized in a table of regulatory assets/liabilities. SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items] SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items] [Line Items] for Tabular disclosure of assets and liabilities that result from rate actions of a regulator. Regulatory assets are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability. SCHEDULE OF REGULATED ASSETS AND LIABILITIES SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Table Text Block] [Table Text Block] for Tabular disclosure of assets and liabilities that result from rate actions of a regulator. Regulatory assets are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability. Statement of Comprehensive Income [Abstract] Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax [Abstract] Change in pension and postemployment benefit plan liability, net of tax of $(351) and $(80), respectively respectively Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Schedule of Regulatory Assets and Liabilities Schedule of Regulatory Assets and Liabilities [Text Block] REVENUE [Abstract] REVENUE [Abstract] Revenues Disaggregated by Source [Table] Revenue from External Customers by Products and Services [Table Text Block] Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Under-recovered purchased-gas costs [Member] Under-recovered purchased-gas costs [Member] Represents the amount of under-recovered purchased-gas costs [Member] Pension and postretirement benefit costs [Member] Pension Costs [Member] Weather normalization [Member] Weather normalization [Member] Weather normalization represents revenue over- or under-recovered through the weather normalization adjustment rider in Kansas. Reacquired debt costs [Member] Loss on Reacquired Debt [Member] MGP Costs [Member] [Member] MGP Costs [Member] [Member] Estimate of manufactured gas plant (MGP) costs expected to be incurred that have been recorded as a regulatory asset. Other regulatory assets [Member] Other regulatory assets [Member] Represents other regulatory assets. Total regulatory assets, net of amortization [Member] Total regulatory assets, net of amortization [Member] Total regulatory assets, net of amortization Over-recovered purchased-gas costs [Member] Over-recovered purchased-gas costs [Member] Represents the amount of over-recovered purchased-gas costs. Ad valorem tax [Member] Ad valorem tax [Member] Ad valorem tax represents an increase in Kansas Gas Service’s taxes above the amount approved in a rate case. Kansas law permits a utility to file a tariff to recover additional ad valorem tax expense incurred above the amount currently recovered in the cost of service rate. This excess amount is recoverable through a surcharge and can be recovered, provided the utility reports the change in rates to the KCC, on an annual basis. Total regulated liabilities [Member] Total regulated liabilities [Member] Represents the amount of total regulated liabilities. Regulatory Assets, Current Regulatory Assets, Current Regulatory Assets, Noncurrent Regulatory Assets, Noncurrent Regulatory Assets Regulatory Assets Regulatory Liability, Current Regulatory Liability, Noncurrent Regulatory Liabilities Regulatory Liabilities Net regulatory assets (liabilities), current Net regulatory assets and liabilities, current The net amount of all current regulatory assets less all current regulatory liabilities as of the end of the period. Net regulatory assets (liabilities), noncurrent Net regulatory assets and liabilities, noncurrent The net amount of noncurrent regulatory assets less all noncurrent regulatory liabilities as of the end of the period. Net Regulatory Assets Net Regulatory Assets Revenue Recognition, Policy [Policy Text Block] Revenue Recognition, Policy [Policy Text Block] EMPLOYEE BENEFIT PLANS Pension and Other Postretirement Benefits Disclosure [Text Block] Basic EPS Calculation Basic EPS Calculation [Abstract] Basic EPS Calculation [Abstract] Net income available for common stock Weighted Average Number of Shares Outstanding, Basic Earnings Per Share, Basic Diluted EPS Calculation Diluted EPS Calculation [Abstract] Diluted EPS Calculation [Abstract] Effect of dilutive securities on income Dilutive Securities, Effect on Basic Earnings Per Share Effect of dilutive securities on shares Weighted Average Number Diluted Shares Outstanding Adjustment Weighted Average Number of Shares Outstanding, Diluted Earnings Per Share, Diluted Statement of Stockholders' Equity [Abstract] Common Stock [Member] Common Stock [Member] Paid-in Capital [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Retained Earnings [Member] Treasury Stock [Member] Treasury Stock [Member] Accumulated Other Comprehensive Income (Loss) [Member] AOCI Attributable to Parent [Member] Shares issued, beginning balance Equity, beginning balance Stockholders' Equity Attributable to Parent Other comprehensive income Common stock issued, shares Stock Issued During Period, Shares, New Issues Common stock issued, value Stock Issued During Period, Value, New Issues Common stock dividends - $0.46 per share Dividends, Common Stock Shares issued, ending balance Equity, ending balance Line of Credit [Member] Line of Credit [Member] Line of Credit Facility Sublimit Line of Credit Facility Sublimit This item represents the amount of sublimit for the issuance of standby letters of credit. Line of Credit Facility Swingline Subfacility Line of Credit Facility Swingline Subfacility This item represents the line of credit facility swingline subfacility. Line of Credit Facility Option to Increase Borrowing Capacity Line of Credit Facility Option to Increase Borrowing Capacity This item represents the total amount the facility my increase to. Line of Credit Facility, Expiration Date Line of Credit Facility, Expiration Date Ratio of Indebtedness to Net Capital Ratio of Indebtedness to Net Capital Commercial paper maximum borrowing capacity Commercial paper maximum borrowing capacity Maximum borrowing capacity under the commercial paper program. Commercial Paper Commercial Paper Short-term Debt Short-term Debt Letters of Credit Outstanding, Amount Letters of Credit Outstanding, Amount Line of Credit Facility, Remaining Borrowing Capacity Line of Credit Facility, Remaining Borrowing Capacity REVENUE [Axis] REVENUE [Axis] Revenues disaggregated by source. REVENUE [Domain] REVENUE [Domain] [Domain] for Revenues disaggregated by source. Natural gas sales to customers [Member] Natural gas sales to customers [Member] Natural gas sales to customers represent revenue from contracts with customers through implied contracts established by our tariff rates approved by the regulatory authorities and includes residential, commercial, industrial, wholesale and public authority customers. For natural gas sales, the customer receives the benefits of our performance when the commodity is received and simultaneously consumed by the customer. The performance obligation is satisfied over time as the customer consumes the natural gas. Transportation revenues [Member] Transportation revenues [Member] Transportation revenues represent revenue from contracts with customers through implied contracts established by our tariff rates approved by the regulatory authorities and tariff-based negotiated contracts. The customer receives the benefits of our performance when the commodity is delivered to the customer and the performance obligation is satisfied over time as the customer consumes the natural gas. Miscellaneous revenues [Member] Miscellaneous revenues [Member] Miscellaneous revenues from contracts with customers represent implied contracts established by our tariff rates approved by the regulatory authorities and includes one-time miscellaneous service charges with the performance obligation satisfied at a point in time when services are rendered to the customer. Other revenues - natural gas sales related [Member] Other revenues - natural gas sales related [Member] Other revenues - natural gas sales related [Member] Other revenues [Member] Other revenues [Member] Other revenues [Member] Unbilled Receivables, Current Unbilled Receivables, Current Regulated Operating Revenue, Gas Regulated Operating Revenue, Other Regulated Operating Revenue Reclassification adjustment, before tax and regulatory adjustments Other comprehensive income (loss) reclassification adjustment, before tax and regulatory adjustments Other comprehensive income (loss) reclassification adjustment, before tax and regulatory adjustments Regulatory adjustments Other comprehensive income (loss) reclassification - Regulatory adjustments Other comprehensive income (loss) reclassification - Regulatory adjustments represent pension and other postretirement benefit costs expected to be recovered through rates and are deferred as part of our regulatory assets. Reclassification adjustment, before tax Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax Reclassification adjustment, Tax Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Tax Reclassification adjustment, net of tax Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Derivative, Nonmonetary Notional Amount Derivative, Nonmonetary Notional Amount Premiums recorded in other current assets on natural gas contracts held Premiums recorded in other current assets on natural gas contracts held The amount of premiums recorded in other current assets on natural gas contracts held Fair value, natural gas call options Fair value, natural gas call options The fair value of purchased natural gas call options held. Fair Value Assets, Transfers between Levels Fair Value Assets, Transfers between Levels Amount of transfers of assets measured on a recurring basis between levels of the fair value hierarchy. Long-term Debt, including current maturities Long-term Debt, Excluding Current Maturities Long-term Debt Long-term Debt Long-term Debt, Fair Value Long-term Debt, Fair Value Comprehensive Income (Loss) Note [Text Block] Comprehensive Income (Loss) Note [Text Block] OTHER INCOME AND OTHER EXPENSE [Axis] OTHER INCOME AND OTHER EXPENSE [Axis] Detail of other income and other expense. OTHER INCOME AND OTHER EXPENSE [Domain] OTHER INCOME AND OTHER EXPENSE [Domain] [Domain] for Detail of other income and other expense. Net periodic cost other than service cost [Member] Net periodic cost other than service cost [Member] Net periodic cost other than service cost [Member] Other, net [Member] Other, net [Member] Other Income and Expense, net Other, net Long-term Debt [Text Block] Long-term Debt [Text Block] Number Of Former Manufactured Gas Sites Where We Own Or Retain Legal Responsibility For Environmental Conditions Number Of Former Manufactured Gas Sites Where We Own Or Retain Legal Responsibility For Environmental Conditions Number of former manufactured gas sites where we own or retain legal responsibility. AAO associated with MGP costs requested amount, cap AAO associated with MGP costs requested amount, cap AAO associated with MGP costs incurred requested amount, cap Regulatory asset expected to be recorded for MGP costs accrued at January 1, 2017 Regulatory asset expected to be recorded for MGP costs accrued at January 1, 2017 Regulatory asset amount expected to be recorded for MGP costs accrued at January 1, 2017 Number of sites where we have completed or addressed removal of the source of soil contamination according to plans approved by KDHE. Number Of Sites Soil Remediation Is Completed Or Near Completion Number of sites soil remediation is completed or near completion. Number of sites with ongoing groundwater monitoring Number of sites with ongoing groundwater monitoring Number of sites where groundwater continues to be monitored in accordance to plans approved by the KDHE. Number of sites where regulatory closure has been achieved Number of sites where regulatory closure has been achieved Number of sites where regulatory closure has been achieved Environmental Reserve Estimate Range, Low Environmental Reserve Estimate Range, Low Potential costs associated with environmental remediation, low-end range. Environmental Reserve Estimate Range, High Environmental Reserve Estimate Range, High Potential costs associated with environmental remediation, high-end range. Environmental Reserve Estimate, Actual Environmental Reserve Estimate, Actual Increase in the reserve recorded for potential costs associated with environmental remediation. Percentage yield of high consequence pipeline areas PercentageYieldOfHighConsequencePipelineAreas Minimum percentage yield required to test pipelines previously untested in high-consequence areas. Assets Assets [Abstract] Property, plant and equipment Property, Plant and Equipment, Net [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 Current assets Assets, Current [Abstract] Cash and cash equivalents Accounts receivable, net Receivables, Net, Current Materials and supplies Materials, Supplies, and Other Natural gas in storage Public Utilities, Inventory Regulatory assets Other current assets Other Assets, Current Total current assets Assets, Current Goodwill and other assets Investments and other assets [Abstract] e5171b7a-202d-b2ed-e1e6-d1c8d50b4c9b Regulatory assets Goodwill Goodwill Other assets Other Assets, Noncurrent Total goodwill and other assets Total goodwill and other assets Sum of the carrying amounts as of the balance sheet date of all assets, excluding property, plant and equipment, that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer. Total assets Assets Equity and Liabilities Liabilities and Equity [Abstract] Equity and long-term debt Capitalization, Long-term Debt and Equity [Abstract] Common stock, $0.01 par value: authorized 250,000,000 shares; issued 52,598,005 shares and outstanding 52,469,880 shares at March 31, 2018; issued 52,598,005 and outstanding 52,312,516 at December 31, 2017 Common Stock, Value, Issued Paid-in Capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Treasury stock, at cost: 128,125 shares at March 31, 2018 and 285,489 shares at December 31, 2017 Treasury Stock, Value Total equity Long-term debt, excluding current maturities and net issuance costs of $7,824 and $8,033, respectively Total equity and long-term debt Capitalization, Long-term Debt and Equity Long-term Debt, Current Maturities Long-term Debt, Current Maturities Current liabilities Liabilities, Current [Abstract] Notes payable Accounts payable Accounts Payable, Current Accrued interest Interest Payable, Current Accrued taxes other than income Accrual for Taxes Other than Income Taxes, Current Accrued liabilities Accrued Liabilities, Current Customer deposits Customer Deposits, Current Other current liabilities Other Liabilities, Current Total current liabilities Liabilities, Current Deferred credits and other liabilities [Abstract] Liabilities, Noncurrent [Abstract] Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Employee benefit obligations Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent Other deferred credits Other Liabilities, Noncurrent Total deferred credits and other liabilities Total deferred credits and other liabilities Total obligations, excluding long-term debt, incurred as part of normal operations that is expected to be repaid beyond the following twelve months or one business cycle. Commitments and contingencies Commitments and Contingencies Total liabilities and equity Liabilities and Equity