ONE Gas (OGS) 10-Q 3 May 16 2016 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2016	Apr. 26, 2016
Document Information [Line Items]
Entity Registrant Name	ONE Gas, Inc.
Entity Central Index Key	1,587,732
Current Fiscal Year End Date	--12-31
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		52,161,391
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016

STATEMENTS OF INCOME

STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Gross Margin
Revenues	$ 508,364	$ 676,531
Cost of natural gas	235,729	413,553
Net margin	272,635	262,978
Operating expenses
Operations and maintenance	106,131	106,561
Depreciation and amortization	34,684	31,630
General taxes	15,747	15,782
Total operating expenses	156,562	153,973
Operating income	116,073	109,005
Other income	18	813
Other expense	(455)	(454)
Interest expense, net	(10,847)	(11,169)
Income before income taxes	104,789	98,195
Income taxes	(40,046)	(37,814)
Net income	$ 64,743	$ 60,381
Earnings per share
Basic	$ 1.23	$ 1.15
Diluted	$ 1.22	$ 1.13
Average shares (thousands)
Basic	52,519	52,707
Diluted	53,107	53,446
Dividends declared per share of stock	$ 0.35	$ 0.30

STATEMENTS OF COMPREHENSIVE INC

STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME Parenthetical - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
STATEMENTS OF COMPREHENSIVE INCOME Parenthetical [Abstract]
Pension and other postemployment benefit plans, tax	$ (72)	$ (88)

STATEMENTS OF COMPREHENSIVE IN4

STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net income	$ 64,743	$ 60,381
Other comprehensive income (loss), net of tax
Change in pension and postemployment benefit plan liability, net of tax of $(72) and $(88), respectively	116	140
Other comprehensive income (loss), net of tax	116	140
Comprehensive income	$ 64,859	$ 60,521

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Property, plant and equipment
Property, plant and equipment	$ 5,196,788	$ 5,132,682
Accumulated depreciation and amortization	1,639,054	1,620,771
Net property, plant and equipment	3,557,734	3,511,911
Current assets
Cash and cash equivalents	52,657	2,433
Accounts receivable, net	195,158	216,343
Materials and supplies	29,708	33,325
Income tax receivable	0	38,877
Natural gas in storage	80,553	142,153
Regulatory assets	42,741	32,925
Other current assets	16,794	16,789
Total current assets	417,611	482,845
Goodwill and other assets
Regulatory assets	421,559	435,863
Goodwill	157,953	157,953
Other assets	43,247	46,193
Total goodwill and other assets	622,759	640,009
Total assets	4,598,104	4,634,765
Equity and long-term debt
Common stock, $0.01 par value: authorized 250,000,000 shares; issued 52,598,005 shares and outstanding 52,161,588 shares at March 31, 2016; issued 52,598,005 and outstanding 52,259,224 at December 31, 2015	526	526
Paid-in Capital	1,754,899	1,764,875
Retained earnings	141,180	95,046
Accumulated other comprehensive income (loss)	(4,285)	(4,401)
Treasury stock, at cost: 436,417 shares at March 31, 2016 and 338,781 shares at December 31, 2015	25,133	14,491
Total equity	1,867,187	1,841,555
Long-term debt, excluding current maturities and net issuance costs of $9,449 and $9,645, respectively	1,191,854	1,191,660
Total equity and long-term debt	3,059,041	3,033,215
Current liabilities
Current maturities of long-term debt	7	7
Notes payable	0	12,500
Accounts payable	59,887	107,482
Accrued interest	7,654	18,873
Accrued taxes other than income	37,784	37,249
Accrued liabilities	15,000	31,470
Customer deposits	62,423	60,325
Regulatory liabilities	20,089	24,615
Other current liabilities	25,749	11,700
Total current liabilities	228,593	304,221
Deferred credits and other liabilities [Abstract]
Deferred income taxes	967,943	951,785
Employee benefit obligations	268,081	272,309
Other deferred credits	74,446	73,235
Total deferred credits and other liabilities	$ 1,310,470	$ 1,297,329
Commitments and contingencies
Total liabilities and equity	$ 4,598,104	$ 4,634,765

BALANCE SHEETS BALANCE SHEETS P

BALANCE SHEETS BALANCE SHEETS Parenthetical - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Common stock, par value per share	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	52,598,005	52,598,005
Common stock, shares outstanding	52,161,588	52,259,224
Treasury stock, shares	436,417	338,781
Debt issuance costs	$ 9,449	$ 9,645

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities
Net income	$ 64,743	$ 60,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	34,684	31,630
Deferred income taxes	16,113	10,460
Share-based compensation expense	4,101	2,484
Provision for doubtful accounts	1,384	896
Changes in assets and liabilities:
Accounts receivable	19,801	17,003
Materials and supplies	3,617	949
Income tax receivable	38,877	38,210
Natural gas in storage	61,600	104,023
Asset removal costs	(14,171)	(8,168)
Accounts payable	(40,060)	(53,777)
Accrued interest	(11,219)	(11,237)
Accrued taxes other than income	535	3,117
Accrued liabilities	(16,470)	(12,371)
Customer deposits	2,098	853
Regulatory assets and liabilities	(593)	63,434
Other assets and liabilities	14,999	(6,797)
Cash provided by operating activities	180,039	241,090
Investing activities
Capital expenditures	(75,261)	(54,914)
Other	392	0
Cash used in investing activities	(74,869)	(54,914)
Financing activities
Repayments of notes payable, net	(12,500)	(42,000)
Repurchase of common stock	(24,066)	0
Issuance of common stock	0	2,156
Dividends paid	(18,380)	(15,773)
Cash used in financing activities	(54,946)	(55,617)
Change in cash and cash equivalents	50,224	130,559
Cash and cash equivalents at beginning of period	2,433	11,943
Cash and cash equivalents at end of period	$ 52,657	$ 142,502

STATEMENT OF CHANGES IN EQUITY

STATEMENT OF CHANGES IN EQUITY - 3 months ended Mar. 31, 2016 - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Shares issued, beginning balance at Dec. 31, 2015	52,598,005	52,598,005
Equity, beginning balance at Dec. 31, 2015	$ 1,841,555	$ 526	$ 1,764,875	$ 95,046	$ (14,491)	$ (4,401)
Net income	64,743	0	0	64,743	0	0
Other comprehensive income	116	0	0	0		116
Repurchase of common stock	(24,066)	$ 0	0	0	(24,066)	0
Common stock issued, shares		0
Common stock issued, value	3,219	$ 0	(10,205)	0	13,424	0
Common stock dividends - $0.35 per share	$ (18,380)	$ 0	229	(18,609)	0	0
Shares issued, ending balance at Mar. 31, 2016	52,598,005	52,598,005
Equity, ending balance at Mar. 31, 2016	$ 1,867,187	$ 526	$ 1,754,899	$ 141,180	$ (25,133)	$ (4,285)

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Notes)	3 Months Ended
	Mar. 31, 2016
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 statement of the results for the interim periods presented. All such adjustments are of a normal recurring nature. The 2015 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, 2016 , are not necessarily indicative of the results that may be expected for a 12-month period. We provide natural gas distribution services to more than 2 million customers 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. 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. 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, 2016 , and 2015 , we had no single external customer from which we received 10 percent or more of our gross revenues. Recently Issued Accounting Standards Update - In March 2016, the FASB issued ASU 2016-12, “Improvements to Employee Share-Based Payment Accounting,” which includes various new aspects to simplify how share-based payments are accounted for and presented in the financial statements. The new standard will modify several aspects of the accounting and reporting for employee share-based payments and related tax accounting impacts, including the presentation in the statements of operations and cash flows. This new guidance is required to be adopted for our interim and annual reports for periods beginning after December 15, 2016. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842),” which prescribes recognizing lease assets and liabilities on the balance sheet and includes disclosure of key information about leasing arrangements. We are evaluating the impact of this issued guidance, which is required to be adopted for our interim and annual reports for periods beginning after December 15, 2018. In August 2015, the FASB issued ASU 2015-15, “Interest-Imputation of Interest (Subtopic 835-30),” which addresses the presentation and subsequent measurement of debt issuance costs associated with line of credit arrangements. We adopted this guidance in the current Quarterly Report, and it did not have an impact on our financial position or results of operations. In April 2015, the FASB issued ASU 2015-03, “Interest-Imputation of Interest,” which requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability. We adopted this guidance in the current Quarterly Report, and have applied the changes retrospectively to all periods presented. We have presented such amounts as a direct deduction from the face amount of our long-term debt, rather than in other assets as a deferred charge in our Balance Sheets. Amortization of the debt issuance costs continues to be reported as interest expense in our Statements of Income. In April 2015, the FASB issued ASU 2015-05, “Intangibles-Goodwill and Other-Internal-Use Software,” which helps entities evaluate the accounting for fees paid by a customer in a cloud computing arrangement. We adopted this guidance prospectively in the current Quarterly Report, and it did not have a material impact on our financial position or results of operations. 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. In July 2015, FASB delayed the effective date for one year. We are evaluating the impact of this issued guidance, which is required to be adopted for our interim and annual reports beginning with the first quarter 2018.

REGULATORY ASSETS AND LIABILITI

REGULATORY ASSETS AND LIABILITIES (Notes)	3 Months Ended
	Mar. 31, 2016
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: March 31, 2016 Current Noncurrent Total ( Thousands of dollars ) Under-recovered purchased-gas costs $ 1,092 $ — $ 1,092 Pension and postemployment benefit costs 23,058 407,444 430,502 Weather normalization 15,678 — 15,678 Reacquired debt costs 812 8,717 9,529 Other 2,101 5,398 7,499 Total regulatory assets, net of amortization 42,741 421,559 464,300 Accumulated removal costs (a) — (6,923 ) (6,923 ) Over-recovered purchased-gas costs (18,852 ) — (18,852 ) Ad valorem tax (1,237 ) — (1,237 ) Total regulatory liabilities (20,089 ) (6,923 ) (27,012 ) Net regulatory assets (liabilities) $ 22,652 $ 414,636 $ 437,288 (a) Included in other deferred credits in our Balance Sheets. December 31, 2015 Current Noncurrent Total ( Thousands of dollars ) Under-recovered purchased-gas costs $ 13,336 $ — $ 13,336 Pension and postemployment benefit costs 15,670 425,175 440,845 Weather normalization 2,198 — 2,198 Reacquired debt costs 812 8,919 9,731 Other 909 1,769 2,678 Total regulatory assets, net of amortization 32,925 435,863 468,788 Accumulated removal costs (a) — (9,032 ) (9,032 ) Over-recovered purchased-gas costs (22,884 ) — (22,884 ) Ad valorem tax (1,731 ) — (1,731 ) Total regulatory liabilities (24,615 ) (9,032 ) (33,647 ) Net regulatory assets (liabilities) $ 8,310 $ 426,831 $ 435,141 (a) Included in other deferred credits in our Balance Sheets. Regulatory assets on our Balance Sheets, as authorized by various regulatory authorities, 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 are subject to review by the respective regulatory authorities during future regulatory 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. In January 2016, as a result of the OCC’s approval of our rate case in Oklahoma, we recorded a regulatory asset of $2.4 million to recover certain information technology costs incurred as a result of our separation from ONEOK in 2014, which will be recovered over four years.

CREDIT FACILITIES (Notes)

CREDIT FACILITIES (Notes)	3 Months Ended
	Mar. 31, 2016
Short-term Debt [Line Items]
Short-term Debt [Text Block]	3. CREDIT FACILITY AND SHORT-TERM NOTES PAYABLE 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. At March 31, 2016 , our debt-to-capital ratio was 39 percent and we were in compliance with all covenants under the ONE Gas Credit Agreement. 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, 2016 , 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.

LONG-TERM DEBT (Notes)

LONG-TERM DEBT (Notes)	3 Months Ended
	Mar. 31, 2016
Long-term Debt, Unclassified [Abstract]
Long-term Debt [Text Block]	4. LONG-TERM DEBT We have senior notes, consisting of $300 million of 2.07 percent senior notes due in 2019 , $300 million of 3.61 percent senior notes due in 2024 and $600 million of 4.658 percent senior notes due in 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.

EQUITY (Notes)

EQUITY (Notes)	3 Months Ended
	Mar. 31, 2016
Class of Stock [Line Items]
Stockholders' Equity Note Disclosure [Text Block]	5. EQUITY Treasury Shares - In the first quarter of 2016, we repurchased approximately 407 thousand shares of our common stock for approximately $24.1 million . Dividends - In May 2016, a dividend of $0.35 per share ( $1.40 per share on an annualized basis) was declared for shareholders of record on May 16, 2016, payable June 1, 2016.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Notes)	3 Months Ended
	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Comprehensive Income (Loss) Note [Text Block]	6. ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following table sets forth the effect of reclassifications from accumulated other comprehensive income (loss) in our Statements of Income for the periods indicated: Three Months Ended Details about Accumulated Other Comprehensive March 31, Affected Line Item in the Income (Loss) Components 2016 2015 Statements of Income ( Thousands of dollars ) Pension and other postemployment benefit plan obligations (a) Amortization of net loss $ 10,037 $ 12,565 Amortization of unrecognized prior service cost (908 ) (373 ) 9,129 12,192 Regulatory adjustments (b) (8,941 ) (11,964 ) 188 228 Income before income taxes (72 ) (88 ) Income tax expense Total reclassifications for the period $ 116 $ 140 Net income (a) These components of accumulated other comprehensive income (loss) are included in the computation of net periodic benefit cost. See Note 8 for additional detail of our net periodic benefit cost . (b) Regulatory adjustments represent pension and other postemployment 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, 2016
EARNINGS PER SHARE [Line Items]
Earnings Per Share [Text Block]	7. 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 basic EPS, 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, 2016 Income Shares Per Share Amount ( Thousands, except per share amounts ) Basic EPS Calculation Net income available for common stock $ 64,743 52,519 $ 1.23 Diluted EPS Calculation Effect of dilutive securities — 588 Net income available for common stock and common stock equivalents $ 64,743 53,107 $ 1.22 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

EMPLOYEE BENEFIT PLANS (Notes)

EMPLOYEE BENEFIT PLANS (Notes)	3 Months Ended
	Mar. 31, 2016
Employee Benefit Plans [Line Items]
EMPLOYEE BENEFIT PLANS	8. EMPLOYEE BENEFIT PLANS The following tables set forth the components of net periodic benefit cost for our pension and other postemployment benefit plans for the periods indicated: Pension Benefits Three Months Ended March 31, 2016 2015 ( Thousands of dollars ) Components of net periodic benefit cost Service cost $ 3,014 $ 3,524 Interest cost 11,387 10,652 Expected return on assets (15,296 ) (15,362 ) Amortization of unrecognized prior service cost — 67 Amortization of net loss 8,886 11,055 Net periodic benefit cost $ 7,991 $ 9,936 Other Postemployment Benefits Three Months Ended March 31, 2016 2015 ( Thousands of dollars ) Components of net periodic benefit cost Service cost $ 638 $ 849 Interest cost 2,627 2,666 Expected return on assets (3,071 ) (2,908 ) Amortization of unrecognized prior service cost (908 ) (440 ) Amortization of net loss 1,151 1,510 Net periodic benefit cost $ 437 $ 1,677 We recover qualified pension benefit plan and other postemployment 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 authorized by the applicable utility commission.

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Notes)	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies [Line Items]
COMMITMENTS AND CONTINGENCIES	9. 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 typically involves 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 the three months ended March 31, 2016 and 2015 . We do not expect expenditures for these matters to have a material adverse effect on our financial condition, results of operations or cash flows. 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. In April 2016, PHMSA published a notice of proposed rulemaking (NPRM) in the Federal Register to revise pipeline safety regulations applicable to the safety of onshore natural gas transmission and gathering pipelines. Proposals include changes to the integrity management requirements and changes to address issues with other requirements. The potential capital and operating expenditures related to the Pipeline Safety, Regulatory Certainty and Job Creation Act are currently being evaluated. The NPRM has a comment period of 60 days. 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 INSTRUMENT

DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Notes)	3 Months Ended
	Mar. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value Disclosures	10. 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 normal sales - Recorded at historical cost - Change in fair value not recognized in earnings 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, 2016 , we had no purchased natural gas call options. At December 31, 2015 , we held purchased natural gas call options for the heating season ended March 2016, with total notional amounts of 17.0 Bcf, for which we paid premiums of $5.8 million , and had a fair value of $0.4 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 purchased-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, 2016 and 2015 . 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 and commercial paper are due upon demand and, therefore, the carrying amounts approximate fair value and are classified as Level 1. The book value of our long-term debt, including current maturities, was $1.2 billion at both March 31, 2016 and December 31, 2015 . The estimated fair value of our long-term debt, including current maturities, was $1.3 billion and $1.2 billion at March 31, 2016 and December 31, 2015 , respectively. The estimated fair value of our Senior Notes at March 31, 2016 and December 31, 2015 , was determined using quoted market prices, and are considered Level 2.

SUMMARY OF SIGNIFICANT ACCOUN19

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2016
Significant Accounting Policies [Line Items]
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.
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, 2016 , and 2015 , 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 March 2016, the FASB issued ASU 2016-12, “Improvements to Employee Share-Based Payment Accounting,” which includes various new aspects to simplify how share-based payments are accounted for and presented in the financial statements. The new standard will modify several aspects of the accounting and reporting for employee share-based payments and related tax accounting impacts, including the presentation in the statements of operations and cash flows. This new guidance is required to be adopted for our interim and annual reports for periods beginning after December 15, 2016. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842),” which prescribes recognizing lease assets and liabilities on the balance sheet and includes disclosure of key information about leasing arrangements. We are evaluating the impact of this issued guidance, which is required to be adopted for our interim and annual reports for periods beginning after December 15, 2018. In August 2015, the FASB issued ASU 2015-15, “Interest-Imputation of Interest (Subtopic 835-30),” which addresses the presentation and subsequent measurement of debt issuance costs associated with line of credit arrangements. We adopted this guidance in the current Quarterly Report, and it did not have an impact on our financial position or results of operations. In April 2015, the FASB issued ASU 2015-03, “Interest-Imputation of Interest,” which requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability. We adopted this guidance in the current Quarterly Report, and have applied the changes retrospectively to all periods presented. We have presented such amounts as a direct deduction from the face amount of our long-term debt, rather than in other assets as a deferred charge in our Balance Sheets. Amortization of the debt issuance costs continues to be reported as interest expense in our Statements of Income. In April 2015, the FASB issued ASU 2015-05, “Intangibles-Goodwill and Other-Internal-Use Software,” which helps entities evaluate the accounting for fees paid by a customer in a cloud computing arrangement. We adopted this guidance prospectively in the current Quarterly Report, and it did not have a material impact on our financial position or results of operations. 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. In July 2015, FASB delayed the effective date for one year. We are evaluating the impact of this issued guidance, which is required to be adopted for our interim and annual reports beginning with the first quarter 2018.

DERIVATIVE FINANCIAL INSTRUME20

DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Policies)	3 Months Ended
	Mar. 31, 2016
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 normal sales - Recorded at historical cost - Change in fair value not recognized in earnings 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 LIABILI21

REGULATORY ASSETS AND LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2016
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: March 31, 2016 Current Noncurrent Total ( Thousands of dollars ) Under-recovered purchased-gas costs $ 1,092 $ — $ 1,092 Pension and postemployment benefit costs 23,058 407,444 430,502 Weather normalization 15,678 — 15,678 Reacquired debt costs 812 8,717 9,529 Other 2,101 5,398 7,499 Total regulatory assets, net of amortization 42,741 421,559 464,300 Accumulated removal costs (a) — (6,923 ) (6,923 ) Over-recovered purchased-gas costs (18,852 ) — (18,852 ) Ad valorem tax (1,237 ) — (1,237 ) Total regulatory liabilities (20,089 ) (6,923 ) (27,012 ) Net regulatory assets (liabilities) $ 22,652 $ 414,636 $ 437,288 (a) Included in other deferred credits in our Balance Sheets. December 31, 2015 Current Noncurrent Total ( Thousands of dollars ) Under-recovered purchased-gas costs $ 13,336 $ — $ 13,336 Pension and postemployment benefit costs 15,670 425,175 440,845 Weather normalization 2,198 — 2,198 Reacquired debt costs 812 8,919 9,731 Other 909 1,769 2,678 Total regulatory assets, net of amortization 32,925 435,863 468,788 Accumulated removal costs (a) — (9,032 ) (9,032 ) Over-recovered purchased-gas costs (22,884 ) — (22,884 ) Ad valorem tax (1,731 ) — (1,731 ) Total regulatory liabilities (24,615 ) (9,032 ) (33,647 ) Net regulatory assets (liabilities) $ 8,310 $ 426,831 $ 435,141 (a) Included in other deferred credits in our Balance Sheets.

ACCUMULATED OTHER COMPREHENSI22

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	3 Months Ended
	Mar. 31, 2016
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) in our Statements of Income for the periods indicated: Three Months Ended Details about Accumulated Other Comprehensive March 31, Affected Line Item in the Income (Loss) Components 2016 2015 Statements of Income ( Thousands of dollars ) Pension and other postemployment benefit plan obligations (a) Amortization of net loss $ 10,037 $ 12,565 Amortization of unrecognized prior service cost (908 ) (373 ) 9,129 12,192 Regulatory adjustments (b) (8,941 ) (11,964 ) 188 228 Income before income taxes (72 ) (88 ) Income tax expense Total reclassifications for the period $ 116 $ 140 Net income (a) These components of accumulated other comprehensive income (loss) are included in the computation of net periodic benefit cost. See Note 8 for additional detail of our net periodic benefit cost . (b) Regulatory adjustments represent pension and other postemployment 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, 2016
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, 2016 Income Shares Per Share Amount ( Thousands, except per share amounts ) Basic EPS Calculation Net income available for common stock $ 64,743 52,519 $ 1.23 Diluted EPS Calculation Effect of dilutive securities — 588 Net income available for common stock and common stock equivalents $ 64,743 53,107 $ 1.22 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

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	3 Months Ended
	Mar. 31, 2016
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 postemployment benefit plans for the periods indicated: Pension Benefits Three Months Ended March 31, 2016 2015 ( Thousands of dollars ) Components of net periodic benefit cost Service cost $ 3,014 $ 3,524 Interest cost 11,387 10,652 Expected return on assets (15,296 ) (15,362 ) Amortization of unrecognized prior service cost — 67 Amortization of net loss 8,886 11,055 Net periodic benefit cost $ 7,991 $ 9,936 Other Postemployment Benefits Three Months Ended March 31, 2016 2015 ( Thousands of dollars ) Components of net periodic benefit cost Service cost $ 638 $ 849 Interest cost 2,627 2,666 Expected return on assets (3,071 ) (2,908 ) Amortization of unrecognized prior service cost (908 ) (440 ) Amortization of net loss 1,151 1,510 Net periodic benefit cost $ 437 $ 1,677

SUMMARY OF SIGNIFICANT ACCOUN25

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) number in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Significant Accounting Policies [Line Items]
Number of natural gas distribution services customers	2
Segment Reporting, Disclosure of Major Customers	0	0

REGULATORY ASSETS AND LIABILI26

REGULATORY ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Mar. 31, 2016	Jan. 31, 2016	Dec. 31, 2015
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current		$ 42,741		$ 32,925
Regulatory Assets, Noncurrent		421,559		435,863
Regulatory Liability, Current		(20,089)		(24,615)
Net regulatory assets (liabilities), current		22,652		8,310
Net regulatory assets (liabilities), noncurrent		414,636		426,831
Net Regulatory Assets		437,288		435,141
Accumulated removal costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current		0		0
Regulatory Liability, Noncurrent		(6,923)		(9,032)
Regulatory Liabilities		(6,923)		(9,032)
Over-recovered purchased-gas costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current		(18,852)		(22,884)
Regulatory Liability, Noncurrent		0		0
Regulatory Liabilities		(18,852)		(22,884)
Ad valorem tax [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current		(1,237)		(1,731)
Regulatory Liability, Noncurrent		0		0
Regulatory Liabilities		(1,237)		(1,731)
Total regulated liabilities [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Liability, Current		(20,089)		(24,615)
Regulatory Liability, Noncurrent		(6,923)		(9,032)
Regulatory Liabilities		(27,012)		(33,647)
Under-recovered purchased-gas costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current		1,092		13,336
Regulatory Assets, Noncurrent		0		0
Regulatory Assets		1,092		13,336
Pension and postretirement benefit costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current		23,058		15,670
Regulatory Assets, Noncurrent		407,444		425,175
Regulatory Assets		430,502		440,845
Weather normalization [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current		15,678		2,198
Regulatory Assets, Noncurrent		0		0
Regulatory Assets		15,678		2,198
Reacquired debt costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current		812		812
Regulatory Assets, Noncurrent		8,717		8,919
Regulatory Assets		9,529		9,731
Other regulatory assets [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current		2,101		909
Regulatory Assets, Noncurrent		5,398		1,769
Regulatory Assets		7,499		2,678
Total regulatory assets, net of amortization [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Current		42,741		32,925
Regulatory Assets, Noncurrent		421,559		435,863
Regulatory Assets		$ 464,300		$ 468,788
Information Technology Costs [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Regulatory Assets, Noncurrent			$ 2,400
Information Technology Costs [Member] | Subsequent Event [Member]
SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]
Estimated Recovery Period	4

CREDIT FACILITIES (Details)

CREDIT FACILITIES (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)
Short-term Debt [Line Items]
Ratio of Indebtedness to Net Capital	0.39
Commercial paper maximum borrowing capacity	$ 700
Letters of Credit Outstanding, Amount	1
Line of Credit Facility, Remaining Borrowing Capacity	$ 699

LONG-TERM DEBT (Details)

LONG-TERM DEBT (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)
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
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
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
Debt Instrument, Interest Rate, Stated Percentage	4.658%

EQUITY (Details)

EQUITY (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016USD ($)$ / sharesshares
Treasury stock acquired, shares | shares	407
Treasury stock acquired, value | $	$ 24,066
Common Stock, Dividends, Per Share, Declared	$ 0.35
Common Stock, Dividends, Declared, Annualized Basis	$ 1.40

ACCUMULATED OTHER COMPREHENSI30

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of net loss	$ 10,037	$ 12,565
Amortization of unrecognized prior service cost	(908)	(373)
Reclassification adjustment, before tax and regulatory adjustments	9,129	12,192
Regulatory adjustments	(8,941)	(11,964)
Reclassification adjustment, before tax	188	228
Reclassification adjustment, Tax	(72)	(88)
Reclassification adjustment, net of tax	$ 116	$ 140

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Basic EPS Calculation
Net income available for common stock	$ 64,743	$ 60,381
Weighted Average Number of Shares Outstanding, Basic	52,519	52,707
Earnings Per Share, Basic	$ 1.23	$ 1.15
Diluted EPS Calculation
Net income available for common stock	$ 64,743	$ 60,381
Effect of dilutive securities on income	$ 0	$ 0
Effect of dilutive securities on shares	588	739
Weighted Average Number of Shares Outstanding, Diluted	53,107	53,446
Earnings Per Share, Diluted	$ 1.22	$ 1.13

EMPLOYEE BENEFIT PLANS (Details

EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Components of net periodic benefit cost:
Amortization of unrecognized prior service cost	$ (908)	$ (373)
Amortization of net loss	10,037	12,565
ONE Gas Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	3,014	3,524
Interest cost	11,387	10,652
Expected return on assets	(15,296)	(15,362)
Amortization of unrecognized prior service cost	0	67
Amortization of net loss	8,886	11,055
Net periodic benefit cost	7,991	9,936
ONE Gas Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	638	849
Interest cost	2,627	2,666
Expected return on assets	(3,071)	(2,908)
Amortization of unrecognized prior service cost	(908)	(440)
Amortization of net loss	1,151	1,510
Net periodic benefit cost	$ 437	$ 1,677

COMMITMENTS AND CONTINGENCIES33

COMMITMENTS AND CONTINGENCIES (Details)	Mar. 31, 2016
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 INSTRUME34

DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Details)	3 Months Ended
	Mar. 31, 2016USD ($)MMcf	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)MMcf
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative, Nonmonetary Notional Amount | MMcf	0		17,000
Premiums recorded in other current assets on natural gas contracts held			$ 5,800,000
Fair Value Assets, Transfers between Levels	$ 0	$ 0
Long-term Debt, including current maturities	1,191,854,000		1,191,660,000
Long-term Debt	1,200,000,000		1,200,000,000
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value, natural gas call options			400,000
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Long-term Debt, Fair Value	$ 1,300,000,000		$ 1,200,000,000