ONE Gas (OGS) 10-Q 30 Apr 15 2015 Q1 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 21, 2015
Document Information [Line Items]
Entity Registrant Name	ONE Gas, Inc.
Entity Central Index Key	1587732
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		52,593,748
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15

STATEMENTS_OF_INCOME

STATEMENTS OF INCOME (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Gross Margin
Revenues	$676,531	$766,178
Cost of natural gas	413,553	506,342
Net margin	262,978	259,836
Operating expenses
Operations and maintenance	106,561	103,499
Depreciation and amortization	31,630	31,460
General taxes	15,782	15,524
Total operating expenses	153,973	150,483
Operating income	109,005	109,353
Other income	813	633
Other expense	-454	-1,148
Interest expense	-11,169	-12,950
Income before income taxes	98,195	95,888
Income taxes	-37,814	-36,812
Net income	$60,381	$59,076
Earnings per share (Note 6)
Basic	$1.15	$1.13
Diluted	$1.13	$1.13
Average shares (thousands)
Basic	52,707	52,334
Diluted	53,446	52,512
Dividends declared per share of stock	$0.30	$0

STATEMENTS_OF_COMPREHENSIVE_IN

STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME Parenthetical (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
STATEMENTS OF COMPREHENSIVE INCOME Parenthetical [Abstract]
Pension and other postretirement benefit plans, tax	($88)	$2,124

STATEMENTS_OF_COMPREHENSIVE_IN1

STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net income	$60,381	$59,076
Other comprehensive income (loss), net of tax
Change in pension and postretirement benefit plan liability, net of tax of $(88) and $2,124, respectively	140	-3,393
Other comprehensive income (loss), net of tax	140	-3,393
Comprehensive income	$60,521	$55,683

BALANCE_SHEETS

BALANCE SHEETS (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Property, plant and equipment
Property, plant and equipment	$4,904,206	$4,850,201
Accumulated depreciation and amortization	1,578,438	1,556,481
Net property, plant and equipment	3,325,768	3,293,720
Current assets
Cash and cash equivalents	142,502	11,943
Accounts receivable, net	308,850	326,749
Income tax receivable	5,590	43,800
Natural gas in storage	81,277	185,300
Regulatory assets (Note 2)	22,322	50,193
Other current assets	43,903	49,516
Total current assets	604,444	667,501
Goodwill and other assets
Regulatory assets (Note 2)	465,049	478,723
Goodwill	157,953	157,953
Other assets	52,274	51,313
Total goodwill and other assets	675,276	687,989
Total assets	4,605,488	4,649,210
Equity and long-term debt
Common stock, $0.01 par value: authorized 250,000,000 shares; issued and outstanding 52,590,112 shares at March 31, 2015; issued and outstanding 52,083,859 at December 31, 2014	526	521
Paid-in Capital	1,759,934	1,758,796
Retained earnings	84,239	39,894
Accumulated other comprehensive income (loss)	-5,034	-5,174
Total equity	1,839,665	1,794,037
Long-term debt, excluding current maturities	1,201,310	1,201,311
Total equity and long-term debt	3,040,975	2,995,348
Current liabilities
Current maturities of long-term debt	6	6
Notes payable	0	42,000
Accounts payable	105,058	159,064
Accrued taxes other than income	47,859	44,742
Accrued liabilities	13,648	26,019
Customer deposits	60,856	60,003
Regulatory liabilities	54,252	32,467
Other current liabilities	18,324	28,132
Total current liabilities	300,003	392,433
Deferred credits and other liabilities [Abstract]
Deferred income taxes	897,458	894,585
Employee benefit obligations	286,654	287,779
Other deferred credits	80,398	79,065
Total deferred credits and other liabilities	1,264,510	1,261,429
Commitments and contingencies (Note 8)
Total liabilities and equity	$4,605,488	$4,649,210

BALANCE_SHEETS_BALANCE_SHEETS_

BALANCE SHEETS BALANCE SHEETS Parenthetical (USD $)	Mar. 31, 2015	Dec. 31, 2014
Common stock, par value per share	$0.01	$0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	52,590,112	52,083,859
Common stock, shares outstanding	52,590,112	52,083,859

STATEMENTS_OF_CASH_FLOWS

STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating activities
Net income	$60,381	$59,076
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31,630	31,460
Deferred income taxes	10,460	152
Share-based compensation expense	2,484	1,794
Provision for doubtful accounts	896	891
Changes in assets and liabilities:
Accounts receivable	17,003	-42,712
Income tax receivable	38,210	0
Natural gas in storage	104,023	84,474
Asset removal costs	-8,168	-8,107
Accounts payable	-53,777	6,091
Current income taxes payable	0	18,965
Accrued taxes other than income	3,117	24,125
Accrued liabilities	-12,371	10,363
Customer deposits	853	1,424
Regulatory assets and liabilities	63,434	11,066
Other assets and liabilities	-17,085	-16,964
Cash provided by operating activities	241,090	182,098
Investing activities
Capital expenditures	-54,914	-65,731
Cash used in investing activities	-54,914	-65,731
Financing activities
Repayments on notes payable, net	-42,000	0
Issuance of debt, net of discounts	0	1,199,994
Long-term debt financing costs	0	-10,903
Cash Payment to ONEOK Upon Separation	0	-1,130,000
Issuance of common stock	2,156	17
Dividends paid	-15,773	0
Cash provided by (used in) financing activities	-55,617	59,108
Change in cash and cash equivalents	130,559	175,475
Cash and cash equivalents at beginning of period	11,943	3,171
Cash and cash equivalents at end of period	$142,502	$178,646

STATEMENT_OF_CHANGES_IN_EQUITY

STATEMENT OF CHANGES IN EQUITY (USD $)	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
In Thousands, except Share data
Retained earnings, beginning balance at Dec. 31, 2014	$39,894			$39,894
Accumulated Other Comprehensive Income (Loss), beginning balance at Dec. 31, 2014	-5,174		1,758,796		-5,174
Total equity, beginning balance at Dec. 31, 2014	1,794,037
Paid-in Capital, beginning balance at Dec. 31, 2014	1,758,796
Common Stock Issued, beginning balance at Dec. 31, 2014	521	521
Common Stock Issued (in shares), beginning balance at Dec. 31, 2014	52,083,859	52,083,859
Cash payment to ONEOK upon separation	0
Net income	60,381	0	0	60,381	0
Other comprehensive income	-140	0	0	0	-140
Common stock issued, shares		506,253
Common stock issued, value	880	5	875	0	0
Common stock dividends - $0.30 per share	-15,773	0	-263	-16,036	0
Retained earnings, ending balance at Mar. 31, 2015	84,239			84,239
Accumulated Other Comprehensive Income (Loss), ending balance at Mar. 31, 2015	-5,034		1,759,934		-5,034
Total equity, ending balance at Mar. 31, 2015	1,839,665
Paid-in Capital, ending balance at Mar. 31, 2015	1,759,934
Common Stock Issued, ending balance at Mar. 31, 2015	$526	$526
Common Stock Issued (in share), ending balance at Mar. 31, 2015	52,590,112	52,590,112

SUMMARY_OF_SIGNIFICANT_ACCOUNT

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Notes)	3 Months Ended
	Mar. 31, 2015
Significant Accounting Policies [Line Items]
SIGNIFICANT ACCOUNTING POLICIES
	1	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Our accompanying unaudited financial statements have been prepared pursuant to the rules and regulations of the SEC. These statements also have been prepared in accordance with GAAP and reflect all adjustments that, in our opinion, are necessary for a fair presentation of the results for the interim periods presented. All such adjustments are of a normal recurring nature. The 2014 year-end balance sheet data was derived from audited financial statements, but does not include all disclosures required by GAAP. These unaudited financial statements should be read in conjunction with the audited financial statements and footnotes in our Annual Report. Due to the seasonal nature of our business, the results of operations for the three months ended March 31, 2015, are not necessarily indicative of the results that may be expected for a 12-month period.
	Separation - Prior to January 31, 2014, ONE Gas, Inc. was a wholly owned subsidiary of ONEOK and comprised its former natural gas distribution business. On January 31, 2014, we became an independent, publicly traded company as a result of a distribution by ONEOK of our common stock to ONEOK’s shareholders. Our common stock began trading “regular-way” under the ticker symbol “OGS” on the NYSE on February 3, 2014.
	We provide natural gas distribution services to more than 2 million customers through our divisions in Oklahoma, Kansas and Texas through Oklahoma Natural Gas, Kansas Gas Service and Texas Gas Service, respectively. We serve residential, commercial, industrial and transportation customers in all three states. In addition, we also provide natural gas distribution services to wholesale and public authority customers.
	Basis of Presentation - Prior to our separation from ONEOK, our financial statements were derived from ONEOK’s financial statements, which included its natural gas distribution business as if we, for accounting purposes, had been a separate company for all periods presented. The financial statements for periods prior to the separation also include expense allocations for certain corporate functions historically performed by ONEOK, including allocations of general corporate expenses related to executive oversight, accounting, treasury, tax, legal, information technology and other services. We believe our assumptions underlying the financial statements, including the assumptions regarding the allocation of general corporate expenses from ONEOK, are reasonable. However, the financial statements may not include all of the actual expenses that would have been incurred by us and may not reflect our results of operations, financial position and cash flows had we been a separate publicly traded company during the periods presented prior to the separation.
	All financial information presented after the separation represents the results of operations, financial position and cash flows of ONE Gas. Accordingly:
	•	Our Statement of Income and Comprehensive Income for the three months ended March 31, 2014, consist of the results of ONE Gas for the two months ended March 31, 2014, and the results of ONE Gas Predecessor for the one month ended January 31, 2014.
	•	Our Statement of Cash Flows for the three months ended March 31, 2014, consists of the results of ONE Gas for the two months ended March 31, 2014, and the results of ONE Gas Predecessor for the one month ended January 31, 2014.
	Use of Estimates - The preparation of our financial statements and related disclosures in accordance with GAAP requires us to make estimates and assumptions with respect to values or conditions that cannot be known with certainty that affect the reported amount of assets and liabilities, and the disclosure of contingent assets and liabilities at the date of the financial statements. These estimates and assumptions also affect the reported amounts of revenue and expenses during the reporting period. Items that may be estimated include, but are not limited to, the economic useful life of assets, fair value of assets and liabilities, provision for doubtful accounts, unbilled revenues for natural gas delivered but for which meters have not been read, natural gas purchased but for which no invoice has been received, provision for income taxes, including any deferred tax valuation allowances, the results of litigation and various other recorded or disclosed amounts.
	We evaluate these estimates on an ongoing basis using historical experience and other methods we consider reasonable based on the particular circumstances. Nevertheless, actual results may differ significantly from the estimates. Any effects on our financial position or results of operations from revisions to these estimates are recorded in the period when the facts that give rise to the revision become known.
	Related-Party Transactions - Prior to our separation from ONEOK on January 31, 2014, we had certain transactions with ONEOK, including, but not limited to, natural gas supply, allocated corporate services, employee benefits, cash management, derivatives and long-term lines of credit. Following the separation, any services we continue to receive from ONEOK are now third-party transactions. The remaining related-party transactions were not material.
	Segments - We operate in one reportable business segment: regulated public utilities that deliver natural gas to residential, commercial, industrial, wholesale, public authority and transportation customers. The accounting policies for our segment are the same as described in Note 1 of our Notes to the Financial Statements in our Annual Report. We evaluate our financial performance principally on operating income. For the three months ended March 31, 2015, and 2014, we had no single external customer from which we received 10 percent or more of our gross revenues.
	Treasury Shares - In February 2015, our Board of Directors authorized us to purchase treasury shares to be used to offset shares issued under our employee and non-employee director equity compensation, dividend reinvestment and employee stock purchase plans. The Board of Directors established an annual limit of $20 million of treasury stock purchases, exclusive of funds received through the dividend reinvestment and employee stock purchase plans. Stock purchases may be made in the open market or in private transactions at times and in amounts that we deem appropriate. There is no guarantee as to the exact number of shares that we may purchase, and we can terminate or limit the program at any time.
	Recently Issued Accounting Standards Update - In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers,” which clarifies and converges the revenue recognition principles under GAAP and International Financial Reporting Standards. We are evaluating the impact of this recently issued guidance, which is required to be adopted for our quarterly and annual reports beginning with the first quarter 2017.

REGULATORY_ASSETS_AND_LIABILIT

REGULATORY ASSETS AND LIABILITIES (Notes)	3 Months Ended
	Mar. 31, 2015
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Schedule of Regulatory Assets and Liabilities
	2	REGULATORY ASSETS AND LIABILITIES
	The tables below present a summary of regulatory assets, net of amortization, and liabilities for the periods indicated:
			31-Mar-15
			Current			Noncurrent			Total
			(Thousands of dollars)
	Pension and postretirement benefit costs (see Note 7)		$	20,218		$	453,382		$	473,600
	Reacquired debt costs		812			9,527			10,339
	Other		1,292			2,140			3,432
	Total regulatory assets, net of amortization		22,322			465,049			487,371
	Accumulated removal costs (a)		—			(15,038		)	(15,038		)
	Weather normalization		(8,740		)	—			(8,740		)
	Over-recovered purchased-gas costs		(44,015		)	—			(44,015		)
	Ad valorem tax		(1,497		)	—			(1,497		)
	Total regulatory liabilities		(54,252		)	(15,038		)	(69,290		)
	Net regulatory assets (liabilities)		$	(31,930	)	$	450,011		$	418,081
	(a) Included in other deferred credits in our Balance Sheets.
			31-Dec-14
			Current			Noncurrent			Total
			(Thousands of dollars)
	Under-recovered purchased-gas costs		$	28,712		$	—		$	28,712
	Pension and postretirement benefit costs		18,108			466,684			484,792
	Reacquired debt costs		812			9,730			10,542
	Other		2,561			2,309			4,870
	Total regulatory assets, net of amortization		50,193			478,723			528,916
	Accumulated removal costs (a)		—			(15,451		)	(15,451		)
	Weather normalization		(16,516		)	—			(16,516		)
	Over-recovered purchased-gas costs		(13,055		)	—			(13,055		)
	Ad valorem tax		(2,896		)	—			(2,896		)
	Total regulatory liabilities		(32,467		)	(15,451		)	(47,918		)
	Net regulatory assets (liabilities)		$	17,726		$	463,272		$	480,998
	(a) Included in other deferred credits in our Balance Sheets.
	Regulatory assets on our Balance Sheets, as authorized by the various regulatory commissions, are probable of recovery. Base rates are designed to provide a recovery of costs during the period rates are in effect, but do not generally provide for a return on investment for amounts we have deferred as regulatory assets. All of our regulatory assets recoverable through base rates are subject to review by the respective regulatory authorities during future rate proceedings. We are not aware of any evidence that these costs will not be recoverable through either riders or base rates, and we believe that we will be able to recover such costs, consistent with our historical recoveries.
	Purchased-gas costs include the costs that have been over- or under-recovered from customers through the purchased-gas cost adjustment mechanisms and also include natural gas utilized in our operations, premiums paid and any cash settlements received from our purchased natural gas call options.

CREDIT_FACILITIES_Notes

CREDIT FACILITIES (Notes)	3 Months Ended
	Mar. 31, 2015
Line of Credit Facility [Line Items]
Short-term Debt [Text Block]
	3	CREDIT FACILITY AND SHORT-TERM NOTES PAYABLE
	ONE Gas Credit Agreement - The ONE Gas Credit Agreement contains certain financial, operational and legal covenants. Among other things, these covenants include maintaining ONE Gas’ 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. At March 31, 2015, our debt-to-capital ratio was 40 percent and we were in compliance with all covenants under the ONE Gas Credit Agreement.
	The ONE Gas Credit Agreement includes a $50 million sublimit for the issuance of standby letters of credit and also features an option to request an increase in the size of the facility to an aggregate of $1.2 billion from $700 million upon satisfaction of customary conditions, including receipt of commitments from new lenders or increased commitments from existing lenders. Borrowings made under the facility are available for general corporate purposes. The ONE Gas Credit Agreement contains provisions for an applicable margin rate and an annual facility fee, both of which adjust with changes in our credit rating. Based on our current credit ratings, borrowings, if any, will accrue interest at LIBOR plus 79.5 basis points, and the annual facility fee is 8 basis points.
	We have a commercial paper program under which we may issue unsecured commercial paper up to a maximum amount of $700 million to fund short-term borrowing needs. The maturities of the commercial paper notes may vary but may not exceed 270 days from the date of issue. The commercial paper notes are generally sold at par less a discount representing an interest factor.
	The ONE Gas Credit Agreement is available to repay the commercial paper notes, if necessary. Amounts outstanding under the commercial paper program reduce the borrowing capacity under the ONE Gas Credit Agreement. At March 31, 2015, we had no short-term borrowings, $1.0 million in letters of credit issued under the ONE Gas Credit Agreement and $699.0 million of remaining credit available under the ONE Gas Credit Agreement.

LONGTERM_DEBT_Notes

LONG-TERM DEBT (Notes)	3 Months Ended
	Mar. 31, 2015
Long-term Debt, Unclassified [Abstract]
Long-term Debt [Text Block]
	4	LONG-TERM DEBT
	Senior Notes - We have senior notes, consisting of $300 million of 2.07 percent senior notes due 2019, $300 million of 3.61 percent senior notes due 2024 and $600 million of 4.658 percent senior notes due 2044 (collectively, our “Senior Notes”). The indenture governing our Senior Notes includes an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25 percent in aggregate principal amount of the outstanding Senior Notes to declare those Senior Notes immediately due and payable in full.

ACCUMULATED_OTHER_COMPREHENSIV

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Notes)	3 Months Ended
	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Comprehensive Income (Loss) Note [Text Block]
	5	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)
	The following table sets forth the effect of reclassifications from accumulated other comprehensive income (loss) on our Statements of Income for the period indicated:
	Details about Accumulated Other Comprehensive		Three Months Ended March 31,						Affected Line Item in the
	Income (Loss) Components		2015			2014			Statements of Income
			(Thousands of dollars)
	Pension and other postretirement benefit plan obligations (a)
	Amortization of net loss		$	12,565		$	8,542
	Amortization of unrecognized prior service cost		(373		)	(303		)
			12,192			8,239
	Regulatory adjustments (b)		(11,964		)	(13,756		)
			228			(5,517		)	Income before income taxes
			(88		)	2,124			Income tax expense
	Total reclassifications for the period		$	140		$	(3,393	)	Net income
	(a) These components of accumulated other comprehensive income (loss) are included in the computation of net periodic benefit cost. See Note 7 for additional detail of our net periodic benefit cost.
	(b) Regulatory adjustments represent pension and other postretirement benefit costs expected to be recovered through rates and are deferred as part of our regulatory assets. See Note 2 for additional disclosures of regulatory assets and liabilities.

EARNINGS_PER_SHARE_Notes

EARNINGS PER SHARE (Notes)	3 Months Ended
	Mar. 31, 2015
EARNINGS PER SHARE [Line Items]
Earnings Per Share [Text Block]
	6	EARNINGS PER SHARE
	Basic EPS is based on net income and is calculated based upon the daily weighted-average number of common shares outstanding during the periods presented. Also, this calculation includes fully vested stock awards that have not yet been issued as common stock. Diluted EPS includes the above, plus unvested stock awards granted under our compensation plans, but only to the extent these instruments dilute earnings per share.
	The following tables set forth the computation of basic and diluted EPS from continuing operations for the periods indicated:
		Three Months Ended March 31, 2015
		Income		Shares	Per Share
					Amount
		(Thousands, except per share amounts)
	Basic EPS Calculation
	Net income available for common stock	$	60,381	52,707	$	1.15
	Diluted EPS Calculation
	Effect of dilutive securities	—		739
	Net income available for common stock and common stock equivalents	$	60,381	53,446	$	1.13
		Three Months Ended March 31, 2014
		Income		Shares	Per Share
					Amount
		(Thousands, except per share amounts)
	Basic EPS Calculation
	Net income available for common stock	$	59,076	52,334	$	1.13
	Diluted EPS Calculation
	Effect of dilutive securities	—		178
	Net income available for common stock and common stock equivalents	$	59,076	52,512	$	1.13
	On January 31, 2014, 51,941,236 shares of our common stock were distributed to ONEOK shareholders in conjunction with the separation. For comparative purposes, and to provide a more meaningful calculation of weighted-average shares outstanding, we have assumed this amount and any shares associated with fully vested stock awards that have not been issued to be outstanding as of the beginning of each period prior to the separation presented in the calculation of weighted-average shares.
	Dividends - In April 2015, a dividend of $0.30 per share ($1.20 per share on an annualized basis) was declared for shareholders of record on May 15, 2015, payable June 1, 2015.

EMPLOYEE_BENEFIT_PLANS_Notes

EMPLOYEE BENEFIT PLANS (Notes)	3 Months Ended
	Mar. 31, 2015
Employee Benefit Plans [Line Items]
EMPLOYEE BENEFIT PLANS
	7	EMPLOYEE BENEFIT PLANS
	The following tables set forth the components of net periodic benefit cost for our pension and other postretirement benefit plans for the periods indicated:
		Pension Benefits
		Three Months Ended			Three Months Ended
		March 31,			March 31,
		2015			2014
		(Thousands of dollars)
	Components of net periodic benefit cost
	Service cost	$	3,524		$	2,768
	Interest cost	10,652			10,948
	Expected return on assets	(15,362		)	(14,965		)
	Amortization of unrecognized prior service cost	67			137
	Amortization of net loss	11,055			7,550
	Net periodic benefit cost	$	9,936		$	6,438
		Other Postretirement Benefits
		Three Months Ended			Three Months Ended
		March 31,			March 31,
		2015			2014
		(Thousands of dollars)
	Components of net periodic benefit cost
	Service cost	$	849		$	1,174
	Interest cost	2,666			2,901
	Expected return on assets	(2,908		)	(2,848		)
	Amortization of unrecognized prior service cost	(440		)	(440		)
	Amortization of net loss	1,510			992
	Net periodic benefit cost	$	1,677		$	1,779
	We recover qualified pension benefit plan and other postretirement benefit plan costs through rates charged to our customers. Certain utility commissions require that the recovery of these costs be based on specific guidelines. The difference between these regulatory-based amounts and the periodic benefit cost calculated pursuant to GAAP is deferred as a regulatory asset or liability and amortized to expense over periods in which this difference will be recovered in rates, as promulgated by the applicable utility commission. Regulatory adjustments to the net periodic benefit cost were not material for the three month periods ended March 31, 2015 and 2014.

COMMITMENTS_AND_CONTINGENCIES_

COMMITMENTS AND CONTINGENCIES (Notes)	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies [Line Items]
COMMITMENTS AND CONTINGENCIES
	8	COMMITMENTS AND CONTINGENCIES
	Environmental Matters - We are subject to multiple historical, wildlife preservation and environmental laws and/or regulations which affect many aspects of our present and future operations. Regulated activities include, but are not limited to, those involving air emissions, storm water and wastewater discharges, handling and disposal of solid and hazardous wastes, wetland preservation, hazardous materials transportation, and pipeline and facility construction. These laws and regulations require us to obtain and/or comply with a wide variety of environmental clearances, registrations, licenses, permits and other approvals. Failure to comply with these laws, regulations, licenses and permits may expose us to fines, penalties and/or interruptions in our operations that could be material to our results of operations. In addition, emission controls and/or other regulatory or permitting mandates under the Clean Air Act and other similar federal and state laws could require unexpected capital expenditures. We cannot assure that existing environmental statutes and regulations will not be revised or that new regulations will not be adopted or become applicable to us. Revised or additional statutes or regulations that result in increased compliance costs or additional operating restrictions could have a material adverse effect on our business, financial condition, results of operations and cash flows.
	We own or retain legal responsibility for the environmental conditions at 12 former manufactured natural gas sites in Kansas. These sites contain potentially harmful materials that are subject to control or remediation under various environmental laws and regulations. A consent agreement with the KDHE governs all work at these sites. The terms of the consent agreement allow us to investigate these sites and set remediation activities based upon the results of the investigations and risk analysis. Remediation involves typically the management of contaminated soils and may involve removal of structures and monitoring and/or remediation of groundwater.
	We have completed or addressed removal of the source of soil contamination at 11 of the 12 sites according to plans approved by the KDHE. Regulatory closure has been achieved at three of the sites. We have begun site assessment at the remaining site where no active remediation has occurred.
	Our expenditures for environmental evaluation, mitigation, remediation and compliance to date have not been significant in relation to our financial position, results of operations or cash flows, and our expenditures related to environmental matters had no material effects on earnings or cash flows during 2015 and 2014. We do not expect to incur material expenditures for these matters in the future.
	Pipeline Safety - We are subject to PHMSA regulations, including integrity-management regulations. PHMSA regulations require pipeline companies operating high-pressure transmission pipelines to perform integrity assessments on pipeline segments that pass through densely populated areas or near specifically designated high-consequence areas. In January 2012, the Pipeline Safety, Regulatory Certainty and Job Creation Act was signed into law. The law increased maximum penalties for violating federal pipeline safety regulations and directs the DOT and the Secretary of Transportation to conduct further review or studies on issues that may or may not be material to us. These issues include, but are not limited to, the following:
	•	an evaluation of whether natural gas pipeline integrity-management requirements should be expanded beyond current high-consequence areas;
	•	a verification of records for pipelines in class 3 and 4 locations and high-consequence areas to confirm maximum allowable operating pressures; and
	•	a requirement to test previously untested pipelines operating above 30 percent yield strength in high-consequence areas.
	The potential capital and operating expenditures related to this legislation, the associated regulations or other new pipeline safety regulations are unknown.
	Legal Proceedings - We are a party to various litigation matters and claims that have arisen in the normal course of our operations. While the results of litigation and claims cannot be predicted with certainty, we believe the reasonably possible losses from such matters, individually and in the aggregate, are not material. Additionally, we believe the probable final outcome of such matters will not have a material adverse effect on our results of operations, financial position or cash flows.

DERIVATIVE_FINANCIAL_INSTRUMEN

DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Notes)	3 Months Ended
	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Disclosures
	9	DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS
	Accounting Treatment - We record all derivative instruments at fair value, with the exception of normal purchases and normal sales that are expected to result in physical delivery. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it, or if regulatory rulings require a different accounting treatment.
	If certain conditions are met, we may elect to designate a derivative instrument as a hedge to mitigate the risk of exposure to changes in fair values or cash flows.
	The table below summarizes the various ways in which we account for our derivative instruments and the impact on our financial statements:
			Recognition and Measurement
	Accounting Treatment		Balance Sheet		Income Statement
	Normal purchases and	-	Recorded at historical cost	-	Change in fair value not recognized in earnings
	normal sales
	Mark-to-market	-	Recorded at fair value	-	Change in fair value recognized in, and
					recoverable through, the purchased-gas cost adjustment mechanisms
	We have not elected to designate any of our derivative instruments as hedges. Premiums paid and any cash settlements received associated with the commodity derivative instruments entered into by us are included in, and recoverable through, the purchased-gas cost adjustment mechanisms.
	Determining Fair Value - We define fair value as the price that would be received from the sale of an asset or the transfer of a liability in an orderly transaction between market participants at the measurement date. We use the market and income approaches to determine the fair value of our assets and liabilities and consider the markets in which the transactions are executed. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date.
	Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below:
	•	Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities;
	•	Level 2 - Significant observable pricing inputs other than quoted prices included within Level 1 that are, either directly or indirectly, observable as of the reporting date. Essentially, this represents inputs that are derived principally from or corroborated by observable market data; and
	•	Level 3 - May include one or more unobservable inputs that are significant in establishing a fair value estimate. These unobservable inputs are developed based on the best information available and may include our own internal data.
	We recognize transfers into and out of the levels as of the end of each reporting period.
	Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety.
	Derivative Instruments -  At March 31, 2015, we had no purchased natural gas call options. At December 31, 2014, we held purchased natural gas call options for the heating season ended March 2015, with total notional amounts of 16.0 Bcf, for which we paid premiums of $6.4 million, and had a fair value of $0.1 million. The premiums paid and any cash settlements received are recorded as part of our unrecovered purchased-gas costs in current regulatory assets as these contracts are included in, and recoverable through, the purchased-gas cost adjustment mechanisms. Additionally, changes in fair value associated with these contracts are deferred as part of our unrecovered purchase gas costs in our Balance Sheets. Our natural gas call options are classified as Level 1 as fair value amounts are based on unadjusted quoted prices in active markets including NYMEX-settled prices. There were no transfers between levels for the three months ended March 31, 2015 and 2014.
	Other Financial Instruments - The approximate fair value of cash and cash equivalents, accounts receivable and accounts payable is equal to book value, due to the short-term nature of these items. Our cash and cash equivalents are comprised of bank and money market accounts and are classified as Level 1.
	Short-term notes payable are due upon demand and, therefore, the carrying amounts approximate fair value and are classified as Level 1. The estimated fair value and book value of our long-term debt, including current maturities, was $1.3 billion and $1.2 billion, respectively, at both March 31, 2015 and December 31, 2014. The estimated fair value of our senior notes at March 31, 2015, was determined using quoted market prices, and are considered Level 2.

SUMMARY_OF_SIGNIFICANT_ACCOUNT1

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2015
Significant Accounting Policies [Line Items]
Basis of Presentation	Basis of Presentation - Prior to our separation from ONEOK, our financial statements were derived from ONEOK’s financial statements, which included its natural gas distribution business as if we, for accounting purposes, had been a separate company for all periods presented. The financial statements for periods prior to the separation also include expense allocations for certain corporate functions historically performed by ONEOK, including allocations of general corporate expenses related to executive oversight, accounting, treasury, tax, legal, information technology and other services. We believe our assumptions underlying the financial statements, including the assumptions regarding the allocation of general corporate expenses from ONEOK, are reasonable. However, the financial statements may not include all of the actual expenses that would have been incurred by us and may not reflect our results of operations, financial position and cash flows had we been a separate publicly traded company during the periods presented prior to the separation.
	All financial information presented after the separation represents the results of operations, financial position and cash flows of ONE Gas. Accordingly:
	•	Our Statement of Income and Comprehensive Income for the three months ended March 31, 2014, consist of the results of ONE Gas for the two months ended March 31, 2014, and the results of ONE Gas Predecessor for the one month ended January 31, 2014.
	•	Our Statement of Cash Flows for the three months ended March 31, 2014, consists of the results of ONE Gas for the two months ended March 31, 2014, and the results of ONE Gas Predecessor for the one month ended January 31, 2014.
Use of Estimates	Use of Estimates - The preparation of our financial statements and related disclosures in accordance with GAAP requires us to make estimates and assumptions with respect to values or conditions that cannot be known with certainty that affect the reported amount of assets and liabilities, and the disclosure of contingent assets and liabilities at the date of the financial statements. These estimates and assumptions also affect the reported amounts of revenue and expenses during the reporting period. Items that may be estimated include, but are not limited to, the economic useful life of assets, fair value of assets and liabilities, provision for doubtful accounts, unbilled revenues for natural gas delivered but for which meters have not been read, natural gas purchased but for which no invoice has been received, provision for income taxes, including any deferred tax valuation allowances, the results of litigation and various other recorded or disclosed amounts.
	We evaluate these estimates on an ongoing basis using historical experience and other methods we consider reasonable based on the particular circumstances. Nevertheless, actual results may differ significantly from the estimates. Any effects on our financial position or results of operations from revisions to these estimates are recorded in the period when the facts that give rise to the revision become known.
Related-Party Transactions	Related-Party Transactions - Prior to our separation from ONEOK on January 31, 2014, we had certain transactions with ONEOK, including, but not limited to, natural gas supply, allocated corporate services, employee benefits, cash management, derivatives and long-term lines of credit. Following the separation, any services we continue to receive from ONEOK are now third-party transactions. The remaining related-party transactions were not material.
Segments	Segments - We operate in one reportable business segment: regulated public utilities that deliver natural gas to residential, commercial, industrial, wholesale, public authority and transportation customers. The accounting policies for our segment are the same as described in Note 1 of our Notes to the Financial Statements in our Annual Report. We evaluate our financial performance principally on operating income. For the three months ended March 31, 2015, and 2014, we had no single external customer from which we received 10 percent or more of our gross revenues.
Recently Issued Accounting Standards Update	Recently Issued Accounting Standards Update - In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers,” which clarifies and converges the revenue recognition principles under GAAP and International Financial Reporting Standards. We are evaluating the impact of this recently issued guidance, which is required to be adopted for our quarterly and annual reports beginning with the first quarter 2017.

DERIVATIVE_FINANCIAL_INSTRUMEN1

DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Policies)	3 Months Ended
	Mar. 31, 2015
Derivatives and Fair Value Measurement [Abstract]
Derivatives	Accounting Treatment - We record all derivative instruments at fair value, with the exception of normal purchases and normal sales that are expected to result in physical delivery. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it, or if regulatory rulings require a different accounting treatment.
	If certain conditions are met, we may elect to designate a derivative instrument as a hedge to mitigate the risk of exposure to changes in fair values or cash flows.
	The table below summarizes the various ways in which we account for our derivative instruments and the impact on our financial statements:
			Recognition and Measurement
	Accounting Treatment		Balance Sheet		Income Statement
	Normal purchases and	-	Recorded at historical cost	-	Change in fair value not recognized in earnings
	normal sales
	Mark-to-market	-	Recorded at fair value	-	Change in fair value recognized in, and
					recoverable through, the purchased-gas cost adjustment mechanisms
	We have not elected to designate any of our derivative instruments as hedges. Premiums paid and any cash settlements received associated with the commodity derivative instruments entered into by us are included in, and recoverable through, the purchased-gas cost adjustment mechanisms.
	Accounting Treatment - We record all derivative instruments at fair value, with the exception of normal purchases and normal sales that are expected to result in physical delivery. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it, or if regulatory rulings require a different accounting treatment.
	If certain conditions are met, we may elect to designate a derivative instrument as a hedge to mitigate the risk of exposure to changes in fair values or cash flows.
	The table below summarizes the various ways in which we account for our derivative instruments and the impact on our financial statements:
			Recognition and Measurement
	Accounting Treatment		Balance Sheet		Income Statement
	Normal purchases and	-	Recorded at historical cost	-	Change in fair value not recognized in earnings
	normal sales
	Mark-to-market	-	Recorded at fair value	-	Change in fair value recognized in, and
					recoverable through, the purchased-gas cost adjustment mechanisms
	We have not elected to designate any of our derivative instruments as hedges. Premiums paid and any cash settlements received associated with the commodity derivative instruments entered into by us are included in, and recoverable through, the purchased-gas cost adjustment mechanisms.
Fair Value Measurement	Determining Fair Value - We define fair value as the price that would be received from the sale of an asset or the transfer of a liability in an orderly transaction between market participants at the measurement date. We use the market and income approaches to determine the fair value of our assets and liabilities and consider the markets in which the transactions are executed. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date.
	Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below:
	•	Level 1 - Unadjusted quoted prices in active markets for identical assets or liabilities;
	•	Level 2 - Significant observable pricing inputs other than quoted prices included within Level 1 that are, either directly or indirectly, observable as of the reporting date. Essentially, this represents inputs that are derived principally from or corroborated by observable market data; and
	•	Level 3 - May include one or more unobservable inputs that are significant in establishing a fair value estimate. These unobservable inputs are developed based on the best information available and may include our own internal data.
	We recognize transfers into and out of the levels as of the end of each reporting period.
	Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety.

REGULATORY_ASSETS_AND_LIABILIT1

REGULATORY ASSETS AND LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2015
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES	The tables below present a summary of regulatory assets, net of amortization, and liabilities for the periods indicated:
		31-Mar-15
		Current			Noncurrent			Total
		(Thousands of dollars)
	Pension and postretirement benefit costs (see Note 7)	$	20,218		$	453,382		$	473,600
	Reacquired debt costs	812			9,527			10,339
	Other	1,292			2,140			3,432
	Total regulatory assets, net of amortization	22,322			465,049			487,371
	Accumulated removal costs (a)	—			(15,038		)	(15,038		)
	Weather normalization	(8,740		)	—			(8,740		)
	Over-recovered purchased-gas costs	(44,015		)	—			(44,015		)
	Ad valorem tax	(1,497		)	—			(1,497		)
	Total regulatory liabilities	(54,252		)	(15,038		)	(69,290		)
	Net regulatory assets (liabilities)	$	(31,930	)	$	450,011		$	418,081
	(a) Included in other deferred credits in our Balance Sheets.
		31-Dec-14
		Current			Noncurrent			Total
		(Thousands of dollars)
	Under-recovered purchased-gas costs	$	28,712		$	—		$	28,712
	Pension and postretirement benefit costs	18,108			466,684			484,792
	Reacquired debt costs	812			9,730			10,542
	Other	2,561			2,309			4,870
	Total regulatory assets, net of amortization	50,193			478,723			528,916
	Accumulated removal costs (a)	—			(15,451		)	(15,451		)
	Weather normalization	(16,516		)	—			(16,516		)
	Over-recovered purchased-gas costs	(13,055		)	—			(13,055		)
	Ad valorem tax	(2,896		)	—			(2,896		)
	Total regulatory liabilities	(32,467		)	(15,451		)	(47,918		)
	Net regulatory assets (liabilities)	$	17,726		$	463,272		$	480,998
	(a) Included in other deferred credits in our Balance Sheets.

ACCUMULATED_OTHER_COMPREHENSIV1

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	3 Months Ended
	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The following table sets forth the effect of reclassifications from accumulated other comprehensive income (loss) on our Statements of Income for the period indicated:
	Details about Accumulated Other Comprehensive	Three Months Ended March 31,						Affected Line Item in the
	Income (Loss) Components	2015			2014			Statements of Income
		(Thousands of dollars)
	Pension and other postretirement benefit plan obligations (a)
	Amortization of net loss	$	12,565		$	8,542
	Amortization of unrecognized prior service cost	(373		)	(303		)
		12,192			8,239
	Regulatory adjustments (b)	(11,964		)	(13,756		)
		228			(5,517		)	Income before income taxes
		(88		)	2,124			Income tax expense
	Total reclassifications for the period	$	140		$	(3,393	)	Net income
	(a) These components of accumulated other comprehensive income (loss) are included in the computation of net periodic benefit cost. See Note 7 for additional detail of our net periodic benefit cost.
	(b) Regulatory adjustments represent pension and other postretirement benefit costs expected to be recovered through rates and are deferred as part of our regulatory assets. See Note 2 for additional disclosures of regulatory assets and liabilities.

EARNINGS_PER_SHARE_Tables

EARNINGS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2015
EARNINGS PER SHARE [Line Items]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following tables set forth the computation of basic and diluted EPS from continuing operations for the periods indicated:
		Three Months Ended March 31, 2015
		Income		Shares	Per Share
					Amount
		(Thousands, except per share amounts)
	Basic EPS Calculation
	Net income available for common stock	$	60,381	52,707	$	1.15
	Diluted EPS Calculation
	Effect of dilutive securities	—		739
	Net income available for common stock and common stock equivalents	$	60,381	53,446	$	1.13
		Three Months Ended March 31, 2014
		Income		Shares	Per Share
					Amount
		(Thousands, except per share amounts)
	Basic EPS Calculation
	Net income available for common stock	$	59,076	52,334	$	1.13
	Diluted EPS Calculation
	Effect of dilutive securities	—		178
	Net income available for common stock and common stock equivalents	$	59,076	52,512	$	1.13

EMPLOYEE_BENEFIT_PLANS_Tables

EMPLOYEE BENEFIT PLANS (Tables)	3 Months Ended
	Mar. 31, 2015
Employee Benefit Plans [Line Items]
Schedule of Net Benefit Costs [Table Text Block]	The following tables set forth the components of net periodic benefit cost for our pension and other postretirement benefit plans for the periods indicated:
		Pension Benefits
		Three Months Ended			Three Months Ended
		March 31,			March 31,
		2015			2014
		(Thousands of dollars)
	Components of net periodic benefit cost
	Service cost	$	3,524		$	2,768
	Interest cost	10,652			10,948
	Expected return on assets	(15,362		)	(14,965		)
	Amortization of unrecognized prior service cost	67			137
	Amortization of net loss	11,055			7,550
	Net periodic benefit cost	$	9,936		$	6,438
		Other Postretirement Benefits
		Three Months Ended			Three Months Ended
		March 31,			March 31,
		2015			2014
		(Thousands of dollars)
	Components of net periodic benefit cost
	Service cost	$	849		$	1,174
	Interest cost	2,666			2,901
	Expected return on assets	(2,908		)	(2,848		)
	Amortization of unrecognized prior service cost	(440		)	(440		)
	Amortization of net loss	1,510			992
	Net periodic benefit cost	$	1,677		$	1,779

SUMMARY_OF_SIGNIFICANT_ACCOUNT2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Treasury Stock Acquired, Repurchase Authorization	$20
Common stock, shares authorized	250,000,000		250,000,000
Number of natural gas distribution services customers	2,000,000
Segment Reporting, Disclosure of Major Customers	0	0

REGULATORY_ASSETS_AND_LIABILIT2

REGULATORY ASSETS AND LIABILITIES (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	$22,322	$50,193
Regulatory Assets, Noncurrent	465,049	478,723
Regulatory Liability, Current	-54,252	-32,467
Net regulatory assets (liabilities), current	-31,930	17,726
Net regulatory assets (liabilities), noncurrent	450,011	463,272
Net Regulatory Assets	418,081	480,998
Accumulated removal costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	0	0
Regulatory Liability, Noncurrent	-15,038	-15,451
Regulatory Liabilities	-15,038	-15,451
Weather normalization [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	-8,740	-16,516
Regulatory Liability, Noncurrent	0	0
Regulatory Liabilities	-8,740	-16,516
Over-recovered purchased-gas costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	-44,015	-13,055
Regulatory Liability, Noncurrent	0	0
Regulatory Liabilities	-44,015	-13,055
Ad valorem tax [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	-1,497	-2,896
Regulatory Liability, Noncurrent	0	0
Regulatory Liabilities	-1,497	-2,896
Total regulated liabilities [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current	-54,252	-32,467
Regulatory Liability, Noncurrent	-15,038	-15,451
Regulatory Liabilities	-69,290	-47,918
Under-recovered purchased-gas costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current		28,712
Regulatory Assets, Noncurrent		0
Regulatory Assets		28,712
Pension and postretirement benefit costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	20,218	18,108
Regulatory Assets, Noncurrent	453,382	466,684
Regulatory Assets	473,600	484,792
Reacquired debt costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	812	812
Regulatory Assets, Noncurrent	9,527	9,730
Regulatory Assets	10,339	10,542
Other regulatory assets [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	1,292	2,561
Regulatory Assets, Noncurrent	2,140	2,309
Regulatory Assets	3,432	4,870
Total regulatory assets, net of amortization [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current	22,322	50,193
Regulatory Assets, Noncurrent	465,049	478,723
Regulatory Assets	$487,371	$528,916

CREDIT_FACILITIES_Details

CREDIT FACILITIES (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Ratio of Indebtedness to Net Capital	0.4
Commercial paper maximum borrowing capacity	$700,000,000
Commercial Paper	0	42,000,000
Letters of Credit Outstanding, Amount	1,000,000
Line of Credit Facility, Remaining Borrowing Capacity	699,000,000
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 Gasb 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, Interest Rate Description	Borrowings, if any, will accrue interest at LIBOR plus 79.5 basis points.
Line of credit facility sublimit	50,000,000
Line Of Credit Facility Option To Increase Borrowing Capacity	1,200,000,000
Line of Credit Facility, Maximum Borrowing Capacity	$700,000,000
Line of Credit Facility, Commitment Fee Description	The annual facility fee is 8 basis points.

LONGTERM_DEBT_Details

LONG-TERM DEBT (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Debt Instrument [Line Items]
Cash payment to ONEOK upon separation	$0	($1,130,000,000)
Note Payable Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Description	The indenture governing our Senior Notes includes an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25 percent in aggregate principal amount of the outstanding Senior Notes to declare those senior notes immediately due and payable in full.
Long-term Debt, Gross	300,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.07%
Note Payable Due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Description	The indenture governing our Senior Notes includes an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25 percent in aggregate principal amount of the outstanding Senior Notes to declare those senior notes immediately due and payable in full.
Long-term Debt, Gross	300,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.61%
Notes Payable Due 2044 [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Description	The indenture governing our Senior Notes includes an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25 percent in aggregate principal amount of the outstanding Senior Notes to declare those senior notes immediately due and payable in full.
Long-term Debt, Gross	$600,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.66%

ACCUMULATED_OTHER_COMPREHENSIV2

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of net loss	$12,565	$8,542
Amortization of unrecognized prior service cost	-373	-303
Reclassification adjustment, before tax and regulatory adjustments	12,192	8,239
Regulatory adjustments	-11,964	-13,756
Reclassification adjustment, before tax	228	-5,517
Reclassification adjustment, Tax	-88	2,124
Reclassification adjustment, net of tax	$140	($3,393)

EARNINGS_PER_SHARE_Details

EARNINGS PER SHARE (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Jun. 30, 2015	Dec. 31, 2014	Jan. 31, 2014
EARNINGS PER SHARE [Line Items]
Common stock, shares issued	52,590,112			52,083,859	51,941,236
Basic EPS Calculation
Net income available for common stock	$60,381	$59,076
Weighted Average Number of Shares Outstanding, Basic	52,707,000	52,334,000
Earnings Per Share, Basic	$1.15	$1.13
Diluted EPS Calculation
Net income available for common stock	60,381	59,076
Effect of dilutive securities on income	$0	$0
Effect of dilutive securities on shares	739,000	178,000
Weighted Average Number of Shares Outstanding, Diluted	53,446,000	52,512,000
Earnings Per Share, Diluted	$1.13	$1.13
Dividend Declared [Member]
Dividends
Common Stock, Dividends, Per Share, Declared			$0.30
Common Stock, Dividends, Declared, Annualized Basis			$1.20

EMPLOYEE_BENEFIT_PLANS_Details

EMPLOYEE BENEFIT PLANS (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Components of net periodic benefit cost:
Amortization of unrecognized prior service cost	($373)	($303)
Amortization of net loss	12,565	8,542
ONE Gas Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	3,524	2,768
Interest cost	10,652	10,948
Expected return on assets	-15,362	-14,965
Amortization of unrecognized prior service cost	67	137
Amortization of net loss	11,055	7,550
Net periodic benefit cost	9,936	6,438
ONE Gas Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	849	1,174
Interest cost	2,666	2,901
Expected return on assets	-2,908	-2,848
Amortization of unrecognized prior service cost	-440	-440
Amortization of net loss	1,510	992
Net periodic benefit cost	$1,677	$1,779

COMMITMENTS_AND_CONTINGENCIES_1

COMMITMENTS AND CONTINGENCIES (Details)	Mar. 31, 2015
Commitments and Contingencies [Line Items]
Number Of Former Manufactured Gas Sites Where We Own Or Retain Legal Responsibility For Environmental Conditions	12
Number of sites where we have completed or addressed removal of the source of soil contamination according to plans approved by KDHE	11
Number of sites where regulatory closure has been achieved	3
Percentage yield of high consequence pipeline areas	30.00%

DERIVATIVE_FINANCIAL_INSTRUMEN2

DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
			MMcf
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative, Nonmonetary Notional Amount			16,000
Premiums recorded in other current assets on natural gas contracts held			$6,400,000
Fair Value Assets, Transfers between Levels	0	0
Long-term Debt, including current maturities	1,201,310,000		1,201,311,000
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value, natural gas call options			100,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Long-term Debt, Fair Value	$1,300,000,000		$1,300,000,000