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SHARE-BASED PAYMENTS (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Feb. 03, 2014
Jan. 31, 2014
Share-based Payments [Line Items]          
Share Price         $ 68.22ogs_VolumeweightedaveragesharepriceofONEOKstockonJanuary312014
Volume-weighted average share price of ONE Gas stock on February 3, 2014       $ 33.50ogs_VolumeweightedaveragesharepriceofONEGasstockonFebruary32014  
Employee Stock Award Program Compensation Expense $ 7,613,000us-gaap_ShareBasedCompensation $ 0us-gaap_ShareBasedCompensation $ 0us-gaap_ShareBasedCompensation    
Employee Stock Purchase Plan [Member]          
Share-based Payments [Line Items]          
Description Subject to certain exclusions, all employees who work at least 20 hours per week are eligible to participate in the ESPP.  Employees can choose to have up to 10 percent of their annual base pay withheld to purchase our common stock, subject to terms and limitations of the plan. The purchase price of the stock is 85 percent of the lower of the average market price of our common stock on the grant date or exercise date.        
Employee Stock Award Program [Member]          
Share-based Payments [Line Items]          
Description Under the program, each time the per-share closing price of our common stock on the NYSE closed for the first time at or above each $1.00 increment above its previous historical high closing price, we issued, for no monetary consideration, one share of our common stock to all eligible employees.        
Restricted Stock Units (RSUs) [Member]          
Share-based Payments [Line Items]          
Share-based awards conversion ratio upon separation         2.04%ogs_Sharebasedawardsconversionratiouponseparation
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Award vesting period 3 years        
Forfeiture rate maximum (in hundredths) 3.00%ogs_ForfeitureRateMaximumInHundredths
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
       
Total compensation cost not yet recognized 2,800,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
       
Total compensation cost not yet recognized, period for recognition 1 year 9 months 18 days        
Performance Unit Awards [Member]          
Share-based Payments [Line Items]          
Share-based awards conversion ratio upon separation         2.04%ogs_Sharebasedawardsconversionratiouponseparation
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Award vesting period 3 years        
Forfeiture rate maximum (in hundredths) 3.00%ogs_ForfeitureRateMaximumInHundredths
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
       
Total compensation cost not yet recognized 4,900,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
       
Total compensation cost not yet recognized, period for recognition 1 year 8 months 12 days        
Employee Stock Purchase Plan [Member]          
Share-based Payments [Line Items]          
Common Stock, Capital Shares Reserved for Future Issuance 700,000us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
       
Maximum allowable percentage of annual base pay withheld to purchase common stock 10.00%ogs_MaximumAllowablePercentageOfAnnualBasePayWithheldToPurchaseOurCommonStock
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
       
Purchase price percentage of the lower of its grant date or exercise date market price (in hundredths) 85.00%ogs_PurchasePricePercentageOfLowerOfItsGrantDateOrExerciseDateMarketPriceInHundredths
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
       
Percent of employees who participated in the Employee Stock Purchase Plan 36.00%ogs_PercentofemployeeswhoparticipatedintheEmployeeStockPurchasePlan
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
       
Shares sold under employee stock purchase plan 51,418ogs_Sharessoldunderemployeestockpurchaseplan
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
       
Share price of shares sold under Employee Stock Purchase Plan in dollars per share $ 32.29ogs_SharepriceofsharessoldunderEmployeeStockPurchasePlanindollarspershare
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
       
Employee Stock Purchase Plan Compensation Expense 400,000us-gaap_EmployeeStockOwnershipPlanESOPCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
2,700,000us-gaap_EmployeeStockOwnershipPlanESOPCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
800,000us-gaap_EmployeeStockOwnershipPlanESOPCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockMember
   
Employee Stock Award Program [Member]          
Share-based Payments [Line Items]          
Shares issued to employees under the Employee Stock Award Program 35,324ogs_SharesissuedtoemployeesundertheEmployeeStockAwardProgram
/ us-gaap_AwardTypeAxis
= us-gaap_StockCompensationPlanMember
       
Employee Stock Award Program Compensation Expense 2,500,000us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_StockCompensationPlanMember
4,200,000us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_StockCompensationPlanMember
1,200,000us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_StockCompensationPlanMember
   
ONEGAS Plan [Member]          
Share-based Payments [Line Items]          
Common Stock, Capital Shares Reserved for Future Issuance 2,800,000us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant 1,300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Share-based compensation expense, net of tax 7,000,000us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Share-based compensation, tax benefit 4,400,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
ONEGAS Plan [Member] | Restricted Stock Units (RSUs) [Member]          
Share-based Payments [Line Items]          
Released to participants prior to separation, number 0ogs_Releasedtoparticipantspriortoseparationnumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Released to participants prior to separation, weighted average fair value $ 0.00ogs_Releasedtoparticipantspriortoseparationweightedaveragefairvalue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Cancelled and replaced upon separation, number (246,683)ogs_Cancelledandreplaceduponseparationnumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Cancelled and replaced upon separation, weighted average fair value $ 19.71ogs_Cancelledandreplaceduponseparationweightedaveragefairvalue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Nonvested beginning balance (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Nonvested beginning balance (in dollars per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Granted (in units) 94,865us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Weighted -average grant date fair value (per unit) $ 33.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Released to participants (in units) (7,217)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Released to participants (in dollars per unit) $ 19.85us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Forfeited (in units) (8,601)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Forfeited (in dollars per unit) $ 25.76us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Nonvested ending balance (in units) 325,730us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Nonvested ending balance (in dollars per unit) $ 23.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Fair value of shares granted (thousands of dollars) 3,149,000ogs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsFairValueOfSharesGranted
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
ONEGAS Plan [Member] | Performance Unit Awards [Member]          
Share-based Payments [Line Items]          
Released to participants prior to separation, number 0ogs_Releasedtoparticipantspriortoseparationnumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Released to participants prior to separation, weighted average fair value $ 0.00ogs_Releasedtoparticipantspriortoseparationweightedaveragefairvalue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Cancelled and replaced upon separation, number (739,521)ogs_Cancelledandreplaceduponseparationnumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Cancelled and replaced upon separation, weighted average fair value $ 14.57ogs_Cancelledandreplaceduponseparationweightedaveragefairvalue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Nonvested beginning balance (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Nonvested beginning balance (in dollars per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Granted (in units) 124,015us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Weighted -average grant date fair value (per unit) $ 35.98us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Forfeited (in units) (15,585)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Forfeited (in dollars per unit) $ 19.15us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Nonvested ending balance (in units) 847,951us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Nonvested ending balance (in dollars per unit) $ 17.62us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Fair value of shares granted (thousands of dollars) 4,462,000ogs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsFairValueOfSharesGranted
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Expected volatility rate 18.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Expected dividend yield 3.37%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
Risk-free interest rate 0.67%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEGASPlanMember
       
ONEOK Plans [Member]          
Share-based Payments [Line Items]          
Share-based compensation expense, net of tax   9,700,000us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
4,800,000us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
   
Share-based compensation, tax benefit   6,100,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
3,000,000us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
   
ONEOK Plans [Member] | Restricted Stock Units (RSUs) [Member]          
Share-based Payments [Line Items]          
Released to participants prior to separation, number (66,960)ogs_Releasedtoparticipantspriortoseparationnumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Released to participants prior to separation, weighted average fair value $ 28.50ogs_Releasedtoparticipantspriortoseparationweightedaveragefairvalue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Cancelled and replaced upon separation, number (70,710)ogs_Cancelledandreplaceduponseparationnumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Cancelled and replaced upon separation, weighted average fair value $ 40.31ogs_Cancelledandreplaceduponseparationweightedaveragefairvalue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Nonvested beginning balance (in units) 137,670us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Nonvested beginning balance (in dollars per unit) $ 34.57us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Granted (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Weighted -average grant date fair value (per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
$ 47.36us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
$ 36.60us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
   
Released to participants (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Released to participants (in dollars per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Forfeited (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Forfeited (in dollars per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Nonvested ending balance (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
137,670us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
     
Nonvested ending balance (in dollars per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
$ 34.57us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
     
Fair value of shares granted (thousands of dollars)   1,323,000ogs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsFairValueOfSharesGranted
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
2,046,000ogs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsFairValueOfSharesGranted
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
   
ONEOK Plans [Member] | Performance Unit Awards [Member]          
Share-based Payments [Line Items]          
Released to participants prior to separation, number (128,458)ogs_Releasedtoparticipantspriortoseparationnumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Released to participants prior to separation, weighted average fair value $ 34.68ogs_Releasedtoparticipantspriortoseparationweightedaveragefairvalue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Cancelled and replaced upon separation, number (136,079)ogs_Cancelledandreplaceduponseparationnumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Cancelled and replaced upon separation, weighted average fair value $ 45.90ogs_Cancelledandreplaceduponseparationweightedaveragefairvalue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Nonvested beginning balance (in units) 264,537us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Nonvested beginning balance (in dollars per unit) $ 40.45us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Granted (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Weighted -average grant date fair value (per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
$ 52.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
$ 42.39us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
   
Forfeited (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Forfeited (in dollars per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
       
Nonvested ending balance (in units) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
264,537us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
     
Nonvested ending balance (in dollars per unit) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
$ 40.45us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
     
Fair value of shares granted (thousands of dollars)   $ 2,926,000ogs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsFairValueOfSharesGranted
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
$ 4,286,000ogs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsFairValueOfSharesGranted
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
   
Expected volatility rate   22.27%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
27.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
   
Expected dividend yield   3.04%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
2.86%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
   
Risk-free interest rate   0.42%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember
0.38%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_PlanNameAxis
= ogs_ONEOKPlansMember