EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Apr. 30, 2022
Components of net periodic benefit cost:
Minimumnumberofyearsofserviceforcertainemployeestobeeligibletoparticipateinsharedwelfareplansthatprovidepostretirementmedicalandlifeinsurancebenefits	5 years
DefinedBenefitPlanAssumptionsUsedToDetermineBenefitObligationsRateofCompensationIncreaseMinimum	3.50%	3.50%
DefinedBenefitPlanAssumptionsUsedToDetermineBenefitObligationsRateofCompensationIncreaseMinimum	4.30%	4.30%
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncreaseMinimum	3.50%	3.60%	3.10%
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncreaseMaximum	4.30%	5.00%	5.00%
Defined Benefit Plan, Plan Assets, Expected Long-Term Rate-of-Return, Description	We determine our discount rates annually. We estimate our discount rate based upon a comparison of the expected cash flows associated with our future payments under our defined benefit pension and other postemployment obligations to a hypothetical bond portfolio created using high-quality bonds that closely match expected cash flows. Bond portfolios are developed by selecting a bond for each of the next 60 years based on the maturity dates of the bonds. Bonds selected to be included in the portfolios are only those rated by Moody’s as AA- or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds.
Regulatory Liability, Noncurrent	$ 467,563	$ 500,478
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	27,000	23,000
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	42,882	36,482
Defined Benefit Plan, Benefit Obligation, Payment for Settlement	39,000
Defined benefit plan, amortization of unrecognized prior service cost	(372)	(525)	$ (289)
Defined benefit plan, amortization of net (gain) loss	5,770	1,960	17,010
AdjustmentToPensionExpenseDueToRemeasurement				$ 7,200
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	(1)	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Before Reclassification Adjustment from AOCI, Tax	(281)	140
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	960	(478)	5,823
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	0	0	0
Regulatory Assets	$ 379,216	$ 363,214
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	7.00%	6.00%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	4.50%	4.50%
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate	2035	2030
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 10,900	$ 12,600	$ 10,900
Cash Surrender Value of Life Insurance	41,500	37,900
Nonservice Costs Member
Components of net periodic benefit cost:
Regulatory Liability, Noncurrent	6,700	2,200
Grosvenor Registered Multi Limited Partnership
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	29,642	40,872
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	quarterly	quarterly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Description	65	65
K2 Institutional Investors I I Limited Partnership
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	$ 30,028	$ 48,254
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 0	$ 0
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Frequency	quarterly	quarterly
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Description	91	91
Investment grade bonds
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	70.00%
US Large Cap Equity
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	13.00%
Alternative Investments
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	7.00%
Developed Foreign Equities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	5.00%
Mid Cap Equities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	3.00%
Emerging Market Equities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	1.00%
Small Cap Equities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	1.00%
Fixed Income Funds
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description	90 percent
Equity Securities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description	10 percent
ONE Gas Pension Plans [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	5.70%	5.30%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.30%	5.60%	3.05%
DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRateAfterRemeasurement			4.55%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets	6.70%	6.75%	6.40%
Defined Benefit Plan, Benefit Obligation	$ 731,117	$ 803,605	$ 784,633
Service cost	6,204	7,242	10,369
Interest cost	41,123	42,428	36,150
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(27,026)	23,015
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(54,099)	(53,713)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	(38,690)	0
Defined Benefit Plan, Plan Assets, Amount	725,401	795,381	768,961
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	22,322	78,827
Defined Benefit Plan, Plan Assets, Contributions by Employer	1,559	1,306
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	(54,099)	(53,713)
Defined Benefit Plan, Plan Assets, Payment for Settlement	(39,762)	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(5,716)	(8,224)
Assets for Plan Benefits, Defined Benefit Plan	14,377	13,409
Liability, Defined Benefit Plan, Current	(1,409)	(1,368)
Employee benefit obligations	(18,684)	(20,265)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	(5,716)	(8,224)
Defined Benefit Plan, Accumulated Benefit Obligation	703,400	772,100
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	9,800
Expected return on assets	(59,027)	(59,518)	(58,528)
Defined benefit plan, amortization of unrecognized prior service cost	372	372	248
Defined benefit plan, amortization of net (gain) loss	5,786	2,008	16,793
Net periodic benefit cost	(5,542)	(7,468)	5,032
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax	1,242	(619)	7,369
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	(1)	1	159
Other Comprehensive (Income) Loss, Defined Benefit Plan, Before Reclassification Adjustment from AOCI, Tax	(281)	140	(1,705)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	(1,720)	(2,091)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	(251,952)	(246,988)
DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossBeforeRegulatoryAssetsAndTaxes	(253,672)	(249,079)
Regulatory Assets	253,517	247,684
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	(155)	(1,395)
Deferred Tax Liabilities, Regulatory Assets	(67)	213
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	(222)	(1,182)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	70,847	101,476	101,511
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase	445	2,095
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period (Decrease)	(2,984)	(618)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Expense	(167)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	1,408	1,562
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(27,880)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(1,451)	(3,074)
Defined Benefit Plan, Benefits Paid	54,100
Defined Benefit Plan, Expected Future Benefit Payment, Year One	52,832
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	53,298
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	53,470
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	54,189
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	54,094
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years	271,532
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	87,330	93,777
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	567,224	600,128
ONE Gas Pension Plans [Member] | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	70,847	101,476
ONE Gas Pension Plans [Member] | Equity Securities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	81,459	88,477
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	81,459	88,477
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Equity Securities | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Government Obligations
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	213,572	204,669
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	213,572	204,669
ONE Gas Pension Plans [Member] | Government Obligations | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Corporate Obligations
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	328,915	366,482
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	328,915	366,482
ONE Gas Pension Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Cash and Money Market Funds
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	30,608	34,277
ONE Gas Pension Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	5,871	5,300
ONE Gas Pension Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	24,737	28,977
ONE Gas Pension Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	11,177	12,350
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	11,177	12,350	14,480
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase	445	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period (Decrease)	0	(618)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Expense	(167)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	1,562
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(1,451)	(3,074)
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	11,177	12,350
ONE Gas Pension Plans [Member] | Other Investments
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	59,670	89,126
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	59,670	89,126	$ 87,031
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period Increase	0	2,095
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Period (Decrease)	(2,984)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Expense	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	1,408	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(27,880)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Pension Plans [Member] | Other Investments | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	$ 59,670	$ 89,126
ONE Gas Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	5.75%	5.40%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.40%	5.70%	3.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets	5.20%	5.55%	5.85%
Defined Benefit Plan, Benefit Obligation	$ 150,984	$ 158,535	$ 168,342
Service cost	610	730	1,274
Interest cost	8,179	9,154	6,448
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	2,631	2,823
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(3,267)	(5,551)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(15,704)	(16,963)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	0
Defined Benefit Plan, Plan Assets, Amount	179,489	181,608	181,877
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	8,404	11,325
Defined Benefit Plan, Plan Assets, Contributions by Employer	0	2,546
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	2,631	2,823
Defined Benefit Plan, Plan Assets, Benefits Paid	(13,154)	(16,963)
Defined Benefit Plan, Plan Assets, Payment for Settlement	0	0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	28,505	23,073
Assets for Plan Benefits, Defined Benefit Plan	28,505	23,073
Liability, Defined Benefit Plan, Current	0	0
Employee benefit obligations	0	0
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	28,505	23,073
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	0
Expected return on assets	(9,134)	(9,728)	(13,181)
Defined benefit plan, amortization of unrecognized prior service cost	0	153	41
Defined benefit plan, amortization of net (gain) loss	(16)	(48)	217
Net periodic benefit cost	(361)	261	(5,201)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	0	0
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax	1,065	(1,457)
DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossBeforeRegulatoryAssetsAndTaxes	1,065	(1,457)
Regulatory Assets	(1,065)	1,457
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	0	0
Defined Benefit Plan, Benefits Paid	15,700
Defined Benefit Plan, Expected Future Benefit Payment, Year One	14,127
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	13,734
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	13,431
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	13,069
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	12,745
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years	58,985
ONE Gas Postretirement Benefit Plans [Member] | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	8,032	7,782
ONE Gas Postretirement Benefit Plans [Member] | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	171,457	173,825
ONE Gas Postretirement Benefit Plans [Member] | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	7,226	7,031
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	7,226	7,031
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Equity Securities | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	41,982	41,863
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	41,982	41,863
ONE Gas Postretirement Benefit Plans [Member] | Government Obligations | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	36,411	38,615
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	36,411	38,615
ONE Gas Postretirement Benefit Plans [Member] | Corporate Obligations | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Cash and Money Market Funds
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	12,973	13,996
ONE Gas Postretirement Benefit Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	806	751
ONE Gas Postretirement Benefit Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	12,167	13,245
ONE Gas Postretirement Benefit Plans [Member] | Cash and Money Market Funds | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	80,897	80,102
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 1 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	0	0
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 2 [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	80,897	80,102
ONE Gas Postretirement Benefit Plans [Member] | Insurance Contracts and Group Annuity Contracts | Fair Value, Inputs, Level 3
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount	$ 0	0
ONE Gas Postretirement Benefit Plans [Member] | Other Investments
Components of net periodic benefit cost:
Defined Benefit Plan, Plan Assets, Amount		181,607
401k Plan
Components of net periodic benefit cost:
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Cost	$ 17,700	16,700	15,300
Nonqualified Plan
Components of net periodic benefit cost:
Other Deferred Compensation Arrangements, Liability, Current and Noncurrent	18,900	16,000
Deferred Compensation Arrangement with Individual, Compensation Expense	$ 2,400	$ 2,300	$ (2,300)