CREDIT FACILITY AND SHORT-TERM NOTES PAYABLE (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Line of Credit Facility [Line Items]
Ratio of Indebtedness to Net Capital	0.41
Commercial paper maximum borrowing capacity	$ 700,000
Commercial Paper	145,000	$ 12,500
Letters of Credit Outstanding, Amount	1,500
Short-term Debt	0
Line of Credit Facility, Remaining Borrowing Capacity	$ 553,500
Short-term Debt, Weighted Average Interest Rate	0.95%	0.70%
Line of Credit [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Covenant Description	The ONE Gas Credit Agreement contains certain financial, operational and legal covenants. Among other things, these covenants include maintaining ONE Gas’ total debt-to-capital ratio of no more than 70 percent at the end of any calendar quarter. The ONE Gas Credit Agreement also contains customary affirmative and negative covenants, including covenants relating to liens, indebtedness of subsidiaries, investments, changes in the nature of business, fundamental changes, transactions with affiliates, burdensome agreements, and use of proceeds. In the event of a breach of certain covenants by ONE Gas, amounts outstanding under the ONE Gas Credit Agreement may become due and payable immediately.
Line of credit facility sublimit	$ 50,000
Line Of Credit Facility Option To Increase Borrowing Capacity	1,200,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 700,000
Line of Credit Facility, Interest Rate Description	Borrowings, if any, will accrue interest at LIBOR plus 79.5 basis points.
Line of Credit Facility, Commitment Fee Description	The annual facility fee is 8 basis points.