Dominion Questar 10-Q 5 Nov 15 2015 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information	9 Months Ended
	Sep. 30, 2015shares
Entity Information [Line Items]
Entity Registrant Name	QUESTAR CORP
Entity Central Index Key	751,652
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding	174,846,306
Questar Gas [Member]
Entity Information [Line Items]
Entity Registrant Name	QUESTAR GAS CO
Entity Central Index Key	68,589
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding	9,189,626
Questar Pipeline [Member]
Entity Information [Line Items]
Entity Registrant Name	QUESTAR PIPELINE CO
Entity Central Index Key	764,044
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding	6,550,843

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
REVENUES
Questar Gas / Revenues from unaffiliated customers	$ 89.3	$ 100.7	$ 605.8	$ 642	$ 924.7	$ 979.4
Wexpro	6.4	9.4	22.8	29.5	28.9	42.6
Questar Pipeline / Revenues from unaffiliated customers	45	47.3	138.3	143.4	185.1	190.6
Other	1.6	0.5	3.3	1.2	4.7	1.4
Total Revenues	142.3	157.9	770.2	816.1	1,143.4	1,214
OPERATING EXPENSES
Cost of sales (excluding operating expenses shown separately)	(52.6)	(42.3)	70.2	81.6	174.9	210.1
Operating and maintenance	38.6	40.5	131.4	139.9	185.7	193.1
General and administrative	26.5	24.7	83.3	84.2	121.8	113.9
Production and other taxes	12.7	16.8	39.3	53.4	52.1	65.6
Depreciation, depletion and amortization	55	50.8	162.9	162.9	213.7	214.3
Abandonment and impairment	0	0	0.1	2	0.1	2
Total Operating Expenses	80.2	90.5	487.2	524	748.3	799
Net gain (loss) from asset sales	0.2	1.5	1.6	1.6	1.2	1.3
OPERATING INCOME (LOSS)	62.3	68.9	284.6	293.7	396.3	416.3
Interest and other income	1.3	2	4.2	5	5.8	5.7
Income from unconsolidated affiliate	0.9	0.9	2.8	2.7	3.6	3.6
Interest expense	(15.7)	(15.7)	(47.4)	(47.3)	(63.2)	(61.5)
INCOME (LOSS) BEFORE INCOME TAXES	48.8	56.1	244.2	254.1	342.5	364.1
Income taxes	(16.2)	(17.5)	(86.4)	(90.1)	(122.2)	(132)
NET INCOME (LOSS)	$ 32.6	$ 38.6	$ 157.8	$ 164	$ 220.3	$ 232.1
Earnings Per Common Share
Basic	$ 0.18	$ 0.22	$ 0.89	$ 0.93	$ 1.25	$ 1.32
Diluted	$ 0.18	$ 0.22	$ 0.89	$ 0.93	$ 1.25	$ 1.32
Weighted-average common shares outstanding
Used in basic calculation	176.2	175.8	176.3	175.8	176.2	175.7
Used in diluted calculation	176.3	176.1	176.5	176.1	176.4	176
Dividends per common share	$ 0.21	$ 0.19	$ 0.63	$ 0.56	$ 0.82	$ 0.74
Questar Gas [Member]
REVENUES
Questar Gas / Revenues from unaffiliated customers	$ 89.3	$ 100.7	$ 605.8	$ 642	$ 924.7	$ 979.4
OPERATING EXPENSES
Cost of natural gas sold (excluding operating expenses shown separately)	44.4	56.8	362	398.6	568.2	625
Operating and maintenance	22.4	22.7	80.3	88.8	114	123.8
General and administrative	12.9	12.3	39.1	39	52.9	53
Depreciation and amortization	13.8	13.5	40.9	40.3	54.2	53.1
Other taxes	4.7	4.8	14.4	14.7	17.5	17.3
Total Operating Expenses	98.2	110.1	536.7	581.4	806.8	872.2
Net gain (loss) from asset sales	0	0	0	0.1	0	0.1
OPERATING INCOME (LOSS)	(8.9)	(9.4)	69.1	60.7	117.9	107.3
Interest and other income	1.3	1.7	3.6	4.3	5.2	5.6
Interest expense	(7)	(7.1)	(21.2)	(21.2)	(28.2)	(26.8)
INCOME (LOSS) BEFORE INCOME TAXES	(14.6)	(14.8)	51.5	43.8	94.9	86.1
Income taxes	5.8	5.7	(19.3)	(16.6)	(34.7)	(32.9)
NET INCOME (LOSS)	(8.8)	(9.1)	32.2	27.2	60.2	53.2
Questar Pipeline [Member]
REVENUES
Questar Pipeline / Revenues from unaffiliated customers	45	47.3	138.3	143.4	185.1	190.6
Revenues from affiliated companies	17.6	17.7	54.8	54.7	73.8	76.6
Total Revenues	62.6	65	193.1	198.1	258.9	267.2
OPERATING EXPENSES
Operating and maintenance	8.9	10.8	27.9	29.3	37.9	39.7
General and administrative	9	8.9	30	28.7	40.2	39
Depreciation and amortization	13.3	13.5	41	40.7	54.8	54
Other taxes	2.1	2.4	6.5	7.1	8.5	9
Cost of sales (excluding operating expenses shown separately)	0.6	0.6	2.3	3	3.3	6.4
Total Operating Expenses	33.9	36.2	107.7	108.8	144.7	148.1
Net gain (loss) from asset sales	0.1	0	0.1	0	(0.4)	0
OPERATING INCOME (LOSS)	28.8	28.8	85.5	89.3	113.8	119.1
Interest and other income	0.1	0.3	0.5	0.7	1	1.3
Income from unconsolidated affiliate	0.9	0.9	2.8	2.7	3.6	3.6
Interest expense	(6.6)	(6.5)	(19.7)	(19.6)	(26.2)	(25.9)
INCOME (LOSS) BEFORE INCOME TAXES	23.2	23.5	69.1	73.1	92.2	98.1
Income taxes	(8)	(8.6)	(24.8)	(26.8)	(33.6)	(36)
NET INCOME (LOSS)	$ 15.2	$ 14.9	$ 44.3	$ 46.3	$ 58.6	$ 62.1

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net income	$ 32.6	$ 38.6	$ 157.8	$ 164	$ 220.3	$ 232.1
Other comprehensive income (loss):
Pension and other postretirement benefits	6.7	3.7	18.7	12.5	(90.7)	156.6
Interest rate cash flow hedge amortization	0.1	0.1	0.5	0.4	0.6	0.5
Commodity cash flow hedge	0.5	0	0.2	0	0.2	0
Income taxes	(2.9)	(1.3)	(7.5)	(4.9)	34.3	(60.2)
Net other comprehensive income (loss)	4.4	2.5	11.9	8	(55.6)	96.9
COMPREHENSIVE INCOME	37	41.1	169.7	172	164.7	329
Questar Pipeline [Member]
Net income	15.2	14.9	44.3	46.3	58.6	62.1
Other comprehensive income (loss):
Interest rate cash flow hedge amortization	0.1	0.1	0.5	0.4	0.6	0.5
Commodity cash flow hedge	0.5	0	0.2	0	0.2	0
Income taxes	(0.3)	0	(0.4)	(0.1)	(0.4)	(0.2)
Net other comprehensive income (loss)	0.3	0.1	0.3	0.3	0.4	0.3
COMPREHENSIVE INCOME	$ 15.5	$ 15	$ 44.6	$ 46.6	$ 59	$ 62.4

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Current Assets
Cash and cash equivalents	$ 0	$ 32	$ 7.3
Accounts receivable, net	62.3	118.1	57.3
Unbilled gas accounts receivable	11.2	93.7	12.8
Gas stored underground	75.1	43.7	69.3
Materials and supplies	29.6	30.4	25.2
Current regulatory assets	89.9	79.6	84.2
Prepaid expenses and other	8.2	11.2	6.3
Deferred income taxes - current	0	5.8	14.7
Total Current Assets	276.3	414.5	277.1
Property, Plant and Equipment	6,129.9	5,961.5	5,852.3
Accumulated depreciation, depletion and amortization	(2,313.9)	(2,226)	(2,185.2)
Net Property, Plant and Equipment	3,816	3,735.5	3,667.1
Investment in unconsolidated affiliate	24.5	24.7	24.9
Noncurrent regulatory assets	22.7	25	18.6
Other noncurrent assets	47.9	50	50.2
TOTAL ASSETS	4,187.4	4,249.7	4,037.9
Current Liabilities
Checks outstanding in excess of cash balances	2.8	0	0
Short-term debt	305	347	234
Accounts payable and accrued expenses	225.9	234.9	225.4
Current regulatory liabilities	3.3	13.4	11
Deferred income taxes - current	2.8	0	0
Current portion of long-term debt and capital lease obligation	276.8	26.1	1
Total Current Liabilities	816.6	621.4	471.4
Long-term debt and capital lease obligation, less current portion	1,004.4	1,257.5	1,283.3
Deferred income taxes	730.9	715.6	718.5
Asset retirement obligations	71	69.3	69.2
Defined benefit pension plan and other postretirement benefits	119.3	185.7	73.3
Noncurrent regulatory liabilities	77.4	69.9	67.9
Customer contributions in aid of construction	26	29.2	29.6
Other noncurrent liabilities	48.5	54.9	45.4
COMMON SHAREHOLDERS' EQUITY
Common stock	465.4	476.8	471.5
Retained earnings	1,017.3	970.7	941.6
Accumulated other comprehensive (loss)	(189.4)	(201.3)	(133.8)
Total Common Shareholders' Equity	1,293.3	1,246.2	1,279.3
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	4,187.4	4,249.7	4,037.9
Questar Gas [Member]
Current Assets
Cash and cash equivalents	0	19.8	0
Accounts receivable, net	38.7	66.4	27.6
Unbilled gas accounts receivable	10.9	93.7	12.8
Accounts receivable from affiliates	67.5	45.2	44.7
Gas stored underground	68.9	40.3	66.8
Materials and supplies	18.2	19.2	14
Current regulatory assets	89.9	78.3	82.6
Prepaid expenses and other	2.7	3.5	2.6
Deferred income taxes - current	0	0	3
Total Current Assets	296.8	366.4	254.1
Property, Plant and Equipment	2,515.6	2,352.3	2,315.1
Accumulated depreciation, depletion and amortization	(806.2)	(780.3)	(770.4)
Net Property, Plant and Equipment	1,709.4	1,572	1,544.7
Noncurrent regulatory assets	19.3	21.3	14.4
Other noncurrent assets	9	9.3	9.3
TOTAL ASSETS	2,034.5	1,969	1,822.5
Current Liabilities
Checks outstanding in excess of cash balances	3.4	0	2.1
Notes payable to Questar	180	119.3	90.8
Accounts payable and accrued expenses	110	111.9	91.8
Accounts payable to affiliates	71.4	78.7	52.2
Dividends payable to Questar	0	9	0
Customer advances	35.3	29.4	23.2
Current regulatory liabilities	0.5	12.5	10.4
Deferred income taxes - current	14.8	6.3	0
Total Current Liabilities	415.4	367.1	270.5
Long-term debt, less current portion	534.5	534.5	534.5
Deferred income taxes	387	377.5	348.5
Noncurrent regulatory liabilities	67.7	60.9	59.1
Customer contributions in aid of construction	26	29.2	29.6
Other noncurrent liabilities	2.2	2.8	2.8
COMMON SHAREHOLDERS' EQUITY
Common stock	23	23	23
Additional paid-in capital	266.4	265.4	264.9
Retained earnings	312.3	308.6	289.6
Total Common Shareholders' Equity	601.7	597	577.5
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	2,034.5	1,969	1,822.5
Questar Pipeline [Member]
Current Assets
Cash and cash equivalents	1.1	7.4	0.4
Notes receivable from Questar	48.2	40.1	35.2
Accounts receivable, net	16.5	17.9	17.3
Accounts receivable from affiliates	47.6	39.2	37.8
Gas stored underground	6.2	3.4	2.5
Materials and supplies	6.9	6.9	6.9
Current regulatory assets	0	1.3	1.6
Prepaid expenses and other	1.4	4.3	1.7
Deferred income taxes - current	1.9	1.9	1.8
Total Current Assets	129.8	122.4	105.2
Property, Plant and Equipment	1,850.9	1,827.7	1,824
Accumulated depreciation, depletion and amortization	(706.7)	(673.9)	(662.9)
Net Property, Plant and Equipment	1,144.2	1,153.8	1,161.1
Investment in unconsolidated affiliate	24.5	24.7	24.9
Noncurrent regulatory and other assets	10.3	10.8	11.4
TOTAL ASSETS	1,308.8	1,311.7	1,302.6
Current Liabilities
Accounts payable and accrued expenses	28	21.7	41.1
Accounts payable to affiliates	11.5	5.8	3.6
Dividends payable to Questar	0	16	0
Current regulatory liabilities	2.8	0.9	0.6
Current portion of long-term debt	25.1	25.1	0
Total Current Liabilities	67.4	69.5	45.3
Long-term debt, less current portion	433.6	433.7	458.8
Deferred income taxes	241.9	241.4	230
Noncurrent regulatory and other liabilities	16.5	15.9	16.1
COMMON SHAREHOLDERS' EQUITY
Common stock	6.6	6.6	6.6
Additional paid-in capital	353	351.4	351
Retained earnings	212	215.7	217.4
Accumulated other comprehensive (loss)	(22.2)	(22.5)	(22.6)
Total Common Shareholders' Equity	549.4	551.2	552.4
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$ 1,308.8	$ 1,311.7	$ 1,302.6

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
OPERATING ACTIVITIES
Net income	$ 157.8	$ 164
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	168.3	169.1
Deferred income taxes	16.5	1.4
Abandonment and impairment	0.1	2
Share-based compensation	8.7	8.5
Net (gain) from asset sales	(1.6)	(1.6)
(Income) from unconsolidated affiliate	(2.8)	(2.7)
Distributions from unconsolidated affiliate and other	3.9	4.1
Changes in operating assets and liabilities	13.1	17.7
Net Cash Provided By Operating Activities	364	362.5
INVESTING ACTIVITIES
Property, plant and equipment	(213.7)	(235.3)
Questar Gas acquisition of gas distribution system	(11.4)	0
Cash used in disposition of assets	(2.8)	(2.6)
Proceeds from disposition of assets	2	9.4
Net Cash Used In Investing Activities	(225.9)	(228.5)
FINANCING ACTIVITIES
Common stock issued	2.5	1
Common stock repurchased	(21.4)	(3.8)
Change in short-term debt	(42)	(42)
Checks outstanding in excess of cash balances	2.8	0
Capital lease obligation repaid	(1)	(0.7)
Dividends paid	(111.2)	(98.5)
Tax benefits from share-based compensation	0.2	1.3
Net Cash Used In Financing Activities	(170.1)	(142.7)
Change in cash and cash equivalents	(32)	(8.7)
Beginning cash and cash equivalents	32	16
Ending cash and cash equivalents	0	7.3
Questar Gas [Member]
OPERATING ACTIVITIES
Net income	32.2	27.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	45	44.2
Deferred income taxes	18	7.7
Share-based compensation	1	1
Net (gain) from asset sales	0	(0.1)
Changes in operating assets and liabilities	24.1	2.6
Net Cash Provided By Operating Activities	120.3	82.6
INVESTING ACTIVITIES
Property, plant and equipment	(153.2)	(138.2)
Questar Gas acquisition of gas distribution system	(11.4)	0
Cash used in disposition of assets	(2.3)	(2.2)
Proceeds from disposition of assets	0.2	0.8
Net Cash Used In Investing Activities	(166.7)	(139.6)
FINANCING ACTIVITIES
Change in notes payable to Questar	60.7	73.1
Checks outstanding in excess of cash balances	3.4	2.1
Dividends paid to Questar	(37.5)	(27)
Net Cash Used In Financing Activities	26.6	48.2
Change in cash and cash equivalents	(19.8)	(8.8)
Beginning cash and cash equivalents	19.8	8.8
Ending cash and cash equivalents	0	0
Questar Pipeline [Member]
OPERATING ACTIVITIES
Net income	44.3	46.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	42.8	42.5
Deferred income taxes	0.2	1.3
Share-based compensation	1.6	1.5
Net (gain) from asset sales	(0.1)	0
(Income) from unconsolidated affiliate	(2.8)	(2.7)
Distributions from unconsolidated affiliate and other	3.5	3.8
Changes in operating assets and liabilities	4.7	4.3
Net Cash Provided By Operating Activities	94.2	97
INVESTING ACTIVITIES
Property, plant and equipment	(28)	(45.3)
Cash used in disposition of assets	(0.5)	(0.4)
Proceeds from disposition of assets	0.1	0.2
Net Cash Used In Investing Activities	(28.4)	(45.5)
FINANCING ACTIVITIES
Change in notes receivable from Questar	(8.1)	(5.8)
Dividends paid to Questar	(64)	(48)
Net Cash Used In Financing Activities	(72.1)	(53.8)
Change in cash and cash equivalents	(6.3)	(2.3)
Beginning cash and cash equivalents	7.4	2.7
Ending cash and cash equivalents	$ 1.1	$ 0.4

Nature of Business (Notes)

Nature of Business (Notes)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Questar Corporation is a Rockies-based integrated natural gas company with three principal complementary and wholly-owned lines of business: • Questar Gas Company (Questar Gas) provides retail natural gas distribution in Utah, Wyoming and Idaho. • Wexpro Company (Wexpro) develops and produces natural gas from cost-of-service reserves for Questar Gas customers. • Questar Pipeline Company (Questar Pipeline) operates interstate natural gas pipelines and storage facilities in the western United States and provides other energy services. Questar is headquartered in Salt Lake City, Utah. Shares of Questar common stock trade on the New York Stock Exchange (NYSE:STR).

Basis of Presentation of Interi

Basis of Presentation of Interim Financial Statements (Notes)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation of Interim Financial Statements	Basis of Presentation of Interim Financial Statements The interim financial statements contain the accounts of Questar and its wholly-owned subsidiaries. The financial statements were prepared in accordance with U.S. generally accepted accounting principles (GAAP), the instructions for Quarterly Reports on Form 10-Q and SEC Regulations S-X and S-K. All significant intercompany accounts and transactions have been eliminated in consolidation. The financial statements reflect all normal, recurring adjustments and accruals that are, in the opinion of management, necessary for a fair presentation of financial position and results of operations for the interim periods presented. Interim financial statements do not include all of the information and notes required by GAAP for audited annual financial statements. These financial statements should be read in conjunction with the financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2014 . The preparation of financial statements and notes in conformity with GAAP requires that management make estimates and assumptions that affect the amounts of revenues, expenses, assets and liabilities, and disclosure of contingent assets and liabilities. Actual results could differ from estimates. The results of operations for the three, nine and 12 months ended September 30, 2015 , are not necessarily indicative of the results that may be expected for the year ending December 31, 2015 . Certain reclassifications were made to prior year information to conform to the current year presentation. Questar and Questar Pipeline use the equity method to account for an investment in an unconsolidated affiliate where they do not have control, but have significant influence. The investment in the unconsolidated affiliate on the Condensed Consolidated Balance Sheets equals Questar Pipeline's proportionate share of equity reported by the unconsolidated affiliate. The investment is assessed for possible impairment when events indicate that the fair value of the investment may be below Questar Pipeline's carrying value. When such a condition is deemed to be other-than-temporary, the carrying value of the investment is written down to its fair value, and the amount of the write-down is included in the determination of net income. White River Hub, LLC, a limited liability company and FERC-regulated transporter of natural gas, is the sole unconsolidated affiliate. Questar Pipeline owns 50% of White River Hub, LLC, and is the operator. In March 2015, Questar Gas purchased Eagle Mountain City's municipal natural gas system for $11.4 million . The city has over 6,500 natural gas customers. Questar Gas obtains the majority of its gas supply from Wexpro's cost-of-service production and pays Wexpro an operator service fee based on the terms of the Wexpro Agreement and the Wexpro II Agreement (Wexpro agreements). Questar Gas also obtains transportation and storage services from Questar Pipeline. These intercompany revenues and expenses are eliminated in the Questar Consolidated Statements of Income by reducing revenues and cost of sales. The underlying costs of Wexpro's production and Questar Pipeline's transportation and storage services are disclosed in other categories in the Consolidated Statements of Income, including operating and maintenance expense and depreciation, depletion and amortization expense. During the second and third quarters of the year, a significant portion of the natural gas from Wexpro production is injected into underground storage. This gas is withdrawn from storage as needed during the heating season in the first and fourth quarters. The cost of natural gas sold is credited with the value of natural gas as it is injected into storage and debited as it is withdrawn from storage. The reported balance in consolidated cost of sales may be a negative amount during the second and third quarters because of the entries to record injection of gas into storage and the elimination of intercompany transactions. The details of Questar's consolidated cost of sales are as follows: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Questar Gas Gas purchases $ 0.3 $ 0.1 $ 43.5 $ 96.7 $ 83.3 $ 169.6 Operator service fee 80.7 82.3 241.0 265.8 324.9 345.2 Transportation and storage 18.1 18.1 58.4 58.8 79.2 80.3 Gathering 5.7 4.5 16.7 14.2 23.5 19.4 Royalties 7.6 14.9 26.4 50.5 36.0 62.4 Storage (injection),net (42.8 ) (39.0 ) (28.6 ) (27.6 ) (2.1 ) (10.3 ) Purchased-gas account adjustment (26.4 ) (25.3 ) 0.9 (63.4 ) 18.5 (46.5 ) Other 1.2 1.2 3.7 3.6 4.9 4.9 Total Questar Gas cost of natural gas sold 44.4 56.8 362.0 398.6 568.2 625.0 Elimination of Questar Gas cost of natural gas sold - affiliated companies (98.2 ) (99.9 ) (295.4 ) (320.6 ) (398.2 ) (422.0 ) Total Questar Gas cost of natural gas sold - unaffiliated parties (53.8 ) (43.1 ) 66.6 78.0 170.0 203.0 Questar Pipeline Total Questar Pipeline cost of sales 0.6 0.6 2.3 3.0 3.3 6.4 Other cost of sales 0.6 0.2 1.3 0.6 1.6 0.7 Total cost of sales $ (52.6 ) $ (42.3 ) $ 70.2 $ 81.6 $ 174.9 $ 210.1

Earnings Per Share (Notes)

Earnings Per Share (Notes)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic earnings per share (EPS) is computed by dividing net income by the weighted-average number of common shares outstanding during the reporting period, which includes vested undistributed restricted stock units (RSUs) and vested undistributed deferred RSUs. Diluted EPS includes the potential increase in the number of outstanding shares that could result from the exercise of in-the-money stock options, the vesting of RSUs with forfeitable dividend equivalents and the distribution of performance shares that are part of the Company's Long-Term Stock Incentive Plan (LTSIP), less shares repurchased under the treasury stock method. Restricted shares and RSUs with nonforfeitable dividends or dividend equivalents are participating securities for the computation of basic EPS under the two-class method. The application of the two-class method has an insignificant impact on the calculation of Questar's basic and diluted EPS. A reconciliation of the components of basic and diluted shares used in the EPS calculation follows: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Weighted-average basic common shares outstanding 176.2 175.8 176.3 175.8 176.2 175.7 Potential number of shares issuable under the Company's LTSIP 0.1 0.3 0.2 0.3 0.2 0.3 Weighted-average diluted common shares outstanding 176.3 176.1 176.5 176.1 176.4 176.0

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Notes)	9 Months Ended
	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Income Comprehensive income, as reported in Questar's Condensed Consolidated Statements of Comprehensive Income, is the sum of net income as reported in the Questar Consolidated Statements of Income and net other comprehensive income (loss) (OCI). OCI includes recognition of the under-funded position of pension and other postretirement benefit plans, interest rate and commodity-based cash flow hedges, changes in the fair value of long-term investment, and the related income taxes. Income or loss is recognized when the pension and other postretirement benefit (OPB) costs are accrued, as the Company records interest expense for hedged interest payments, as the Company reaches settlement of commodity-based hedges and when the long-term investment is sold. Details of the changes in the components of consolidated accumulated other comprehensive income (loss) (AOCI), net of income taxes, as reported in Questar's Condensed Consolidated Balance Sheets, are shown in the tables below. The tables also disclose details of income taxes related to each component of OCI. Pension and OPB Interest rate cash flow hedges Commodity cash flow hedges Long-term investment Total 3 Months Ended September 30, 2015 (in millions) AOCI at beginning of period $ (171.4 ) $ (22.3 ) $ (0.2 ) $ 0.1 $ (193.8 ) OCI before reclassifications — — 0.5 — 0.5 Reclassified from AOCI (1) 6.7 0.1 — — 6.8 Income taxes OCI before reclassifications — — (0.2 ) — (0.2 ) Reclassified from AOCI (2) (2.6 ) (0.1 ) — — (2.7 ) Total income taxes (2.6 ) (0.1 ) (0.2 ) — (2.9 ) Net other comprehensive income 4.1 — 0.3 — 4.4 AOCI at end of period $ (167.3 ) $ (22.3 ) $ 0.1 $ 0.1 $ (189.4 ) Pension and OPB Interest rate cash flow hedges Long-term investment Total 3 Months Ended September 30, 2014 (in millions) AOCI at beginning of period $ (113.7 ) $ (22.7 ) $ 0.1 $ (136.3 ) Reclassified from AOCI (1) 3.7 0.1 — 3.8 Income taxes Reclassified from AOCI (2) (1.3 ) — — (1.3 ) Total income taxes (1.3 ) — — (1.3 ) Net other comprehensive income 2.4 0.1 — 2.5 AOCI at end of period $ (111.3 ) $ (22.6 ) $ 0.1 $ (133.8 ) Pension and OPB Interest rate cash flow hedges Commodity cash flow hedges Long-term investment Total 9 Months Ended September 30, 2015 (in millions) AOCI at beginning of period $ (178.9 ) $ (22.5 ) $ — $ 0.1 $ (201.3 ) OCI before reclassifications — — 0.2 — 0.2 Reclassified from AOCI (1) 18.7 0.5 — — 19.2 Income taxes OCI before reclassifications — — (0.1 ) — (0.1 ) Reclassified from AOCI (2) (7.1 ) (0.3 ) — — (7.4 ) Total income taxes (7.1 ) (0.3 ) (0.1 ) — (7.5 ) Net other comprehensive income 11.6 0.2 0.1 — 11.9 AOCI at end of period $ (167.3 ) $ (22.3 ) $ 0.1 $ 0.1 $ (189.4 ) Pension and OPB Interest rate cash flow hedges Long-term investment Total 9 Months Ended September 30, 2014 (in millions) AOCI at beginning of period $ (119.0 ) $ (22.9 ) $ 0.1 $ (141.8 ) Reclassified from AOCI (1) 12.5 0.4 — 12.9 Income taxes Reclassified from AOCI (2) (4.8 ) (0.1 ) — (4.9 ) Total income taxes (4.8 ) (0.1 ) — (4.9 ) Net other comprehensive income 7.7 0.3 — 8.0 AOCI at end of period $ (111.3 ) $ (22.6 ) $ 0.1 $ (133.8 ) (1) Interest rate cash flow hedge amounts are included in their entirety as charges to interest expense on the Consolidated Statements of Income. (2) Income tax reclassifications related to interest rate cash flow hedge amounts are included in their entirety as credits to income taxes on the Consolidated Statements of Income. Pension and other postretirement benefit AOCI reclassifications are included in the computation of net periodic pension and postretirement benefit costs. See Note 9 for additional details. Comprehensive income, as reported in Questar Pipeline's Condensed Consolidated Statements of Comprehensive Income, is the sum of net income as reported in the Questar Pipeline Consolidated Statements of Income and net OCI. OCI includes interest rate and commodity-based cash flow hedges and the related income taxes. Income or loss is recognized as the company records interest expense for hedged interest payments and as the company reaches settlement of commodity-based hedges. Disclosures above regarding interest rate and commodity-based cash flow hedges, including related income taxes and income statement reclassification effects, apply to Questar Pipeline.

Asset Retirement Obligations (N

Asset Retirement Obligations (Notes)	9 Months Ended
	Sep. 30, 2015
Asset Retirement Obligation [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations Questar records an asset retirement obligation (ARO) along with an increase to the carrying value of the related property, plant and equipment when there is a legal obligation associated with the retirement of a tangible long-lived asset. Questar's AROs apply primarily to abandonment costs associated with gas and oil wells, production facilities and certain other properties. The Company has not recorded AROs on a majority of its long-lived transportation and distribution assets because the Company does not have a legal obligation to restore the area surrounding abandoned assets. The fair value of retirement costs is estimated by Company personnel based on abandonment costs of similar properties available to field operations and depreciated over the life of the related assets. Revisions to estimates result from material changes in the expected timing or amount of cash flows associated with AROs. Income or expense resulting from the settlement of ARO liabilities is included in net gain (loss) from asset sales on the Consolidated Statements of Income. The ARO liability is adjusted to present value each period through an accretion calculation using a credit-adjusted risk-free interest rate. Changes in Questar's AROs from the Condensed Consolidated Balance Sheets were as follows: 9 Months Ended September 30, 2015 2014 (in millions) AROs at beginning of year $ 69.3 $ 67.7 Accretion 2.5 2.5 Liabilities incurred 0.6 0.7 Revisions in estimated cash flows 5.7 0.4 Liabilities settled (7.1 ) (2.1 ) AROs at end of period $ 71.0 $ 69.2 Wexpro collects from Questar Gas and deposits in trust certain funds related to AROs. The funds are recorded as other noncurrent assets and used to satisfy retirement obligations as the properties are abandoned. The accounting treatment of reclamation activities associated with AROs for properties administered under the Wexpro agreements is defined in a guideline letter between Wexpro and the Utah Division of Public Utilities and the staff of the Wyoming Public Service Commission.

Fair Value Measurements (Notes)

Fair Value Measurements (Notes)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Questar complies with the accounting standards for fair value measurements and disclosures. The standards establish a fair value hierarchy. Level 1 inputs are unadjusted quoted prices for identical assets or liabilities in active markets that the Company has the ability to access at the measurement date. Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 3 inputs are unobservable inputs for the asset or liability. Fair value accounting standards also apply to certain nonfinancial assets and liabilities that are measured at fair value on a nonrecurring basis. Questar The following table discloses the carrying amount, estimated fair value and level within the fair value hierarchy of certain financial instruments not disclosed in other notes to Questar's financial statements in this Quarterly Report: Hierarchy Level of Fair Value Estimates Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Sept. 30, 2015 Sept. 30, 2014 Dec. 31, 2014 (in millions) Financial assets Cash and cash equivalents 1 $ — $ — $ 7.3 $ 7.3 $ 32.0 $ 32.0 Long-term investment 1 14.0 14.0 15.8 15.8 15.7 15.7 Financial liabilities Checks outstanding in excess of cash balances 1 2.8 2.8 — — — — Short-term debt 1 305.0 305.0 234.0 234.0 347.0 347.0 Long-term debt, including current portion 2 1,243.8 1,323.5 1,245.7 1,364.0 1,245.2 1,356.1 The long-term investment is recorded at fair value and consists of money market and short-term bond index mutual funds held in Wexpro's trust (see Note 5). The fair value of the long-term investment is based on quoted prices for the underlying funds. The fair value of fixed-rate long-term debt is based on the discounted present value of cash flows using the Company's current credit risk-adjusted borrowing rates. Questar Gas The following table discloses the carrying amount, estimated fair value and level within the fair value hierarchy of certain financial instruments not disclosed in other notes to Questar Gas's financial statements in this Quarterly Report: Hierarchy Level of Fair Value Estimates Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Sept. 30, 2015 Sept. 30, 2014 Dec. 31, 2014 (in millions) Financial assets Cash and cash equivalents 1 $ — $ — $ — $ — $ 19.8 $ 19.8 Financial liabilities Checks outstanding in excess of cash balances 1 3.4 3.4 2.1 2.1 — — Notes payable to Questar 1 180.0 180.0 90.8 90.8 119.3 119.3 Long-term debt 2 534.5 588.7 534.5 602.8 534.5 607.2 The carrying amounts of notes payable to Questar approximate fair value because of their short maturities and market-based interest rates. The fair value of fixed-rate long-term debt is based on the discounted present value of cash flows using Questar Gas's current credit risk-adjusted borrowing rates. Questar Pipeline The following table discloses the carrying amount, estimated fair value and level within the fair value hierarchy of certain financial instruments not disclosed in other notes to Questar Pipeline's financial statements in this Quarterly Report: Hierarchy Level of Fair Value Estimates Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Sept. 30, 2015 Sept. 30, 2014 Dec. 31, 2014 (in millions) Financial assets Cash and cash equivalents 1 $ 1.1 $ 1.1 $ 0.4 $ 0.4 $ 7.4 $ 7.4 Notes receivable from Questar 1 48.2 48.2 35.2 35.2 40.1 40.1 Financial liabilities Long-term debt, including current portion 2 458.7 484.1 458.8 505.0 458.8 495.5 The carrying amounts of notes receivable from Questar approximate fair value because of their short maturities and market-based interest rates. The fair value of fixed-rate long-term debt is based on the discounted present value of cash flows using Questar Pipeline's current credit risk-adjusted borrowing rates.

Derivatives and Hedging (Notes)

Derivatives and Hedging (Notes)	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging	Derivatives and Hedging Questar and its subsidiaries may enter into derivative instruments to manage exposure to changes in current and future market interest rates. Questar Pipeline entered into forward starting swaps totaling $150.0 million in the second and third quarters of 2011 in anticipation of issuing $180.0 million of notes in December 2011. Settlement of these swaps required payments of $37.3 million in the fourth quarter of 2011 because of declines in interest rates. These swaps qualified as cash flow hedges and the settlement payments are being amortized to interest expense over the 30 -year life of the debt. See the Condensed Consolidated Statements of Comprehensive Income and Note 4 for details regarding reclassifications of AOCI related to deferred interest rate cash flow hedge losses to interest expense for the three and nine months ended September 30, 2015 and September 30, 2014 . Reclassifications into earnings of amounts reported in AOCI will continue while interest expense is recorded for the hedged interest payments through maturity in 2041 . Pre-tax net losses of $0.5 million are expected to be reclassified from AOCI to the Consolidated Statements of Income in the next 12 months . There was a $0.2 million derivative asset at September 30, 2015 , and no derivative assets or liabilities outstanding at September 30, 2014 or December 31, 2014 .

Operations by Line of Business

Operations by Line of Business (Notes)	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Operations by Line of Business	Operations by Line of Business Questar's three principal complementary lines of business include Questar Gas, which provides retail natural gas distribution in Utah, Wyoming and Idaho; Wexpro, which develops and produces natural gas from cost-of-service reserves for Questar Gas customers; and Questar Pipeline, which operates interstate natural gas pipelines and storage facilities and provides other energy services. Line-of-business information is presented according to senior management's basis for evaluating performance and considering differences in the nature of products, services and regulation, among other factors. Following is a summary of operations by line of business: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Revenues from Unaffiliated Customers Questar Gas $ 89.3 $ 100.7 $ 605.8 $ 642.0 $ 924.7 $ 979.4 Wexpro 6.4 9.4 22.8 29.5 28.9 42.6 Questar Pipeline 45.0 47.3 138.3 143.4 185.1 190.6 Other 1.6 0.5 3.3 1.2 4.7 1.4 Total $ 142.3 $ 157.9 $ 770.2 $ 816.1 $ 1,143.4 $ 1,214.0 Revenues from Affiliated Companies Wexpro $ 80.7 $ 82.3 $ 241.1 $ 266.3 $ 325.1 $ 345.9 Questar Pipeline 17.6 17.7 54.8 54.7 73.8 76.6 Total $ 98.3 $ 100.0 $ 295.9 $ 321.0 $ 398.9 $ 422.5 Operating Income (Loss) Questar Gas $ (8.9 ) $ (9.4 ) $ 69.1 $ 60.7 $ 117.9 $ 107.3 Wexpro 40.7 47.2 124.2 141.5 166.0 187.3 Questar Pipeline 28.8 28.8 85.5 89.3 113.8 119.1 Corporate and other 1.7 2.3 5.8 2.2 (1.4 ) 2.6 Total $ 62.3 $ 68.9 $ 284.6 $ 293.7 $ 396.3 $ 416.3 Net Income (Loss) Questar Gas $ (8.8 ) $ (9.1 ) $ 32.2 $ 27.2 $ 60.2 $ 53.2 Wexpro 26.9 31.1 82.5 93.0 112.3 121.4 Questar Pipeline 15.2 14.9 44.3 46.3 58.6 62.1 Corporate and other (0.7 ) 1.7 (1.2 ) (2.5 ) (10.8 ) (4.6 ) Total $ 32.6 $ 38.6 $ 157.8 $ 164.0 $ 220.3 $ 232.1

Employee Benefits (Notes)

Employee Benefits (Notes)	9 Months Ended
	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Employee Benefits	Employee Benefits The Company has a noncontributory defined benefit pension plan covering a majority of its employees and postretirement medical and life insurance plans providing coverage to less than half of its employees. Employees hired or rehired after June 30, 2010, are not eligible for the noncontributory defined benefit pension plan and employees hired or rehired after December 31, 1996, are not eligible for the postretirement medical plan and are not eligible to receive basic life insurance once they retire. Questar is subject to and complies with minimum-required and maximum-allowed annual contribution levels for its qualified pension plan, as determined by the Employee Retirement Income Security Act and the Internal Revenue Code. The 2015 estimated net cost for the qualified pension plan is $19.0 million . This cost does not include any costs of pension settlement accounting. Questar expects to record noncash settlement accounting costs in the fourth quarter of 2015 because the pension plan has settled benefits for some terminated vested employees and is offering lump-sum benefits to retirees starting benefits on or after January 1, 2015. The amount of the settlement accounting costs has not yet been determined. The projected 2015 qualified pension plan funding is $69.0 million . The Company also has a nonqualified pension plan that covers a group of management employees in addition to the noncontributory qualified pension plan. The nonqualified pension plan provides for defined benefit payments upon retirement of the management employee, above the benefit limit defined by the Internal Revenue Service (IRS) for the qualified plan. The nonqualified pension plan is unfunded; benefits are paid from the Company's general funds. The 2015 estimated net cost for the nonqualified pension plan is $3.9 million . Components of the qualified and nonqualified net periodic pension cost are listed in the table below: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Service cost $ 3.7 $ 2.9 $ 10.5 $ 8.9 $ 13.4 $ 12.4 Interest cost 8.3 8.3 24.5 25.0 32.9 32.6 Expected return on plan assets (12.3 ) (11.4 ) (35.6 ) (32.7 ) (46.5 ) (42.2 ) Prior service cost 0.1 0.1 0.1 0.4 0.3 0.7 Recognized net actuarial loss 6.3 3.7 17.7 11.6 21.5 18.8 Net pension cost $ 6.1 $ 3.6 $ 17.2 $ 13.2 $ 21.6 $ 22.3 The Company currently estimates a $2.1 million net cost for postretirement benefits other than pensions in 2015 , before accretion of a regulatory liability. Net periodic postretirement benefit cost components are listed in the table below: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Service cost $ 0.1 $ 0.2 $ 0.4 $ 0.5 $ 0.5 $ 0.6 Interest cost 0.8 0.9 2.6 2.9 3.5 3.8 Expected return on plan assets (0.7 ) (0.8 ) (2.3 ) (2.3 ) (3.0 ) (3.0 ) Recognized net actuarial loss (gain) 0.3 (0.1 ) 0.9 0.5 1.1 1.3 Accretion of regulatory liability 0.3 0.2 0.7 0.6 0.9 0.6 Net postretirement benefit cost $ 0.8 $ 0.4 $ 2.3 $ 2.2 $ 3.0 $ 3.3

Contingencies (Notes)

Contingencies (Notes)	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies Questar and each of its subsidiaries are involved in various commercial, environmental, and regulatory claims. Litigation and other legal proceedings arise in the ordinary course of business. Except as stated below concerning the QEP lawsuit, management does not believe any litigation or other legal proceedings individually or in the aggregate will have a material adverse effect on Questar's, Questar Gas's or Questar Pipeline's financial position, results of operations or cash flows. A liability is recorded for a loss contingency when its occurrence is probable and its amount can be reasonably estimated. If some amount within a range of possible outcomes appears to be a better estimate than any other amount within the range, that amount is recorded. Otherwise, the minimum amount in the range is recorded. Disclosures are provided for contingencies reasonably likely to occur, which would have a material adverse effect on Questar's, Questar Gas's or Questar Pipeline's financial position, results of operations or cash flows. Some of the claims involve highly complex issues relating to liability, damages and other matters subject to substantial uncertainties and, therefore, the probability of liability or an estimate of loss cannot be reasonably determined. Litigation On May 1, 2012, Questar Gas Company filed a legal action against QEP Field Services Company, a subsidiary of QEP Resources, Inc. The case, entitled Questar Gas Company v. QEP Field Services Company , was filed in the Third District Court in Salt Lake County, Utah. Questar Gas believes certain charges of QEP Field Services Company for gathering services exceed the amounts contemplated under a Gas Gathering Agreement, effective September 1, 1993, pertaining to certain gas produced by Wexpro Company under the Wexpro Agreement. Questar Gas is alleging breach of contract by QEP Field Services Company and is seeking an accounting, damages and a declaratory judgment relating to the services and charges under the Gas Gathering Agreement. The charges under the Gas Gathering Agreement are included in Questar Gas's rates as part of its purchased-gas costs. QEP Field Services Company filed an answer and counterclaim alleging that Questar Gas breached the Agreement by failing to allow QEP Field Services to gather and process gas from certain wells located in two fields in the state of Wyoming. On August 13, 2013, QEP Field Services Company assigned its interest in the Gas Gathering Agreement to QEPM Gathering I, LLC, a subsidiary of the general partner of the master limited partnership QEP Midstream Partners. Plaintiffs have filed an amended complaint naming QEP Midstream Partners, LP; QEP Midstream Partners GP, LLC; QEP Midstream Partners Operating, LLC; and QEPM Gathering I, LLC (QEP MLP Entities). QEP Field Services and Tesoro Logistics LP (Tesoro) entered into a Membership Interest Purchase Agreement dated October 19, 2014, to transfer QEP Field Services’ interest in the QEP MLP Entities and related assets and liabilities of QEP Field Services to Tesoro, including control of this legal action. Tesoro closed on the transaction for QEP’s midstream business on December 2, 2014. On December 2, 2014, the court issued a memorandum decision granting two motions for partial summary judgment for breach of contract filed by Questar Gas. The court found QEP Field Services Company breached the Gas Gathering Agreement by overcharging Questar Gas in its gathering rates. The court also denied two motions for partial summary judgment filed by QEP Field Services to reduce or limit contract damages. The court also denied cross-motions for partial summary judgment filed by both parties relating to another claim of breach of contract. The issues raised by the cross-motions, QEP Field Services’ counterclaim and damages on all claims are currently reserved for trial. Trial has been scheduled for April 2016. While Questar Gas intends to vigorously pursue its legal rights, the claims and counterclaims involve complex legal issues and uncertainties that make it difficult to predict the outcome of the case and therefore management cannot determine at this time whether this litigation may have a material adverse effect on its financial position, results of operations or cash flows. In February 2015, a trial was held in the case of Rocky Mountain Resources and Robert N. Floyd v. QEP Energy Company and Wexpro Company , Ninth Judicial District, County of Sublette, State of Wyoming, Case No. 2011-7816. Plaintiffs allege they are entitled to a 4% overriding royalty interest (ORRI) in a so-called replacement state oil and gas lease ultimately assigned to Wexpro and QEP Energy Company (QEP) in the Pinedale Field. Wexpro and QEP believe the former state leases subject to the ORRI expired and a new lease was issued by the State of Wyoming unburdened by the 4% ORRI. A jury decision was reached on February 13, 2015, that awarded the Plaintiffs $14.1 million from Wexpro and $16.2 million from QEP. Wexpro and QEP plan to file an appeal of the case to the Wyoming Supreme Court. Wexpro has accrued its estimate of liability in the case. Any additional royalties will be recovered from Questar Gas’s customers.

Asset Impairments (Notes)

Asset Impairments (Notes)	9 Months Ended
	Sep. 30, 2015
Wexpro Impairment [Abstract]
Asset Impairments	Asset Impairments During the second quarter of 2014, Wexpro recorded a pre-tax abandonment and impairment charge of $2.0 million for its share of the remaining investment in the Brady field. Wexpro concluded that the field had reached the end of its productive life because it was no longer economical to produce natural gas and oil. In the second quarter of 2015, Wexpro sold its share of the Brady field and recognized a gain of $1.4 million .

Accounting Developments (Notes)

Accounting Developments (Notes)	9 Months Ended
	Sep. 30, 2015
Recent Accounting Developments [Abstract]
Recent Accounting Developments	Accounting Developments In August 2015, the FASB issued ASU 2015-15, Interest—Imputation of Interest (Subtopic 835-30): Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements—Amendments to SEC Paragraphs Pursuant to Staff Announcement at June 18, 2015 EITF Meeting (SEC Update) . This update adds SEC staff guidance to the Codification that the SEC staff will not object to an entity presenting the costs of securing line-of-credit arrangements as an asset, regardless of whether there are any outstanding borrowings. The guidance was issued in response to questions that arose after the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30) - Simplifying the Presentation of Debt Issuance Costs, in April 2015. The Company is currently evaluating the ASU's effect on its financial position. In August 2015, the FASB issued ASU 2015-14. This update defers the effective date of ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , which the FASB issued in May of 2014, by one year. ASU 2014-09 replaces most of the existing revenue guidance with a single set of principles, including changes in recognition and disclosure requirements. The revised effective date will be January 1, 2018 and early adoption is permitted beginning January 1, 2017. The new guidance must be applied retrospectively for each prior period presented or via a cumulative effect upon the date of initial application. The Company is currently evaluating the ASU's effect on its financial position, results of operations or cash flows, as well as which transition approach it will take. In July 2015, the FASB issued ASU 2015-11, Inventory (Topic 330) . The ASU states that inventory should be measured at the lower of cost and net realizable value. The guidance will be effective beginning January 1, 2017 and will be applied prospectively. The Company is currently evaluating the ASU's effect on its financial position, results of operations and cash flows. In May 2015, the FASB issued ASU 2015-07, Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (Topic 820) . The ASU removes the requirement to categorize within the fair value hierarchy all investments for which fair value is measured using the net asset value per share practical expedient and it removes the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the net asset value per share practical expedient. The guidance will be effective beginning January 1, 2016 and early adoption is permitted. The new guidance must be applied retrospectively to all periods presented. The Company is currently evaluating the ASU's effect on its disclosures. In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30) . The ASU simplifies the presentation of debt issuance costs by requiring that the 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. The guidance will be effective beginning January 1, 2016 and early adoption is permitted. The new guidance must be applied retrospectively for each prior period presented. The Company is currently evaluating the ASU's effect on its financial position.

Basis of Presentation of Inte18

Basis of Presentation of Interim Financial Statements (Policies)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Questar Corporation is a Rockies-based integrated natural gas company with three principal complementary and wholly-owned lines of business: • Questar Gas Company (Questar Gas) provides retail natural gas distribution in Utah, Wyoming and Idaho. • Wexpro Company (Wexpro) develops and produces natural gas from cost-of-service reserves for Questar Gas customers. • Questar Pipeline Company (Questar Pipeline) operates interstate natural gas pipelines and storage facilities in the western United States and provides other energy services. Questar is headquartered in Salt Lake City, Utah. Shares of Questar common stock trade on the New York Stock Exchange (NYSE:STR).
Investment in Unconsolidated Affiliate	Questar and Questar Pipeline use the equity method to account for an investment in an unconsolidated affiliate where they do not have control, but have significant influence. The investment in the unconsolidated affiliate on the Condensed Consolidated Balance Sheets equals Questar Pipeline's proportionate share of equity reported by the unconsolidated affiliate. The investment is assessed for possible impairment when events indicate that the fair value of the investment may be below Questar Pipeline's carrying value. When such a condition is deemed to be other-than-temporary, the carrying value of the investment is written down to its fair value, and the amount of the write-down is included in the determination of net income. White River Hub, LLC, a limited liability company and FERC-regulated transporter of natural gas, is the sole unconsolidated affiliate. Questar Pipeline owns 50% of White River Hub, LLC, and is the operator.
Earnings Per Share	Basic earnings per share (EPS) is computed by dividing net income by the weighted-average number of common shares outstanding during the reporting period, which includes vested undistributed restricted stock units (RSUs) and vested undistributed deferred RSUs. Diluted EPS includes the potential increase in the number of outstanding shares that could result from the exercise of in-the-money stock options, the vesting of RSUs with forfeitable dividend equivalents and the distribution of performance shares that are part of the Company's Long-Term Stock Incentive Plan (LTSIP), less shares repurchased under the treasury stock method. Restricted shares and RSUs with nonforfeitable dividends or dividend equivalents are participating securities for the computation of basic EPS under the two-class method. The application of the two-class method has an insignificant impact on the calculation of Questar's basic and diluted EPS.
Comprehensive Income - Questar	Comprehensive income, as reported in Questar's Condensed Consolidated Statements of Comprehensive Income, is the sum of net income as reported in the Questar Consolidated Statements of Income and net other comprehensive income (loss) (OCI). OCI includes recognition of the under-funded position of pension and other postretirement benefit plans, interest rate and commodity-based cash flow hedges, changes in the fair value of long-term investment, and the related income taxes. Income or loss is recognized when the pension and other postretirement benefit (OPB) costs are accrued, as the Company records interest expense for hedged interest payments, as the Company reaches settlement of commodity-based hedges and when the long-term investment is sold.
Comprehensive Income - Questar Pipeline	Comprehensive income, as reported in Questar Pipeline's Condensed Consolidated Statements of Comprehensive Income, is the sum of net income as reported in the Questar Pipeline Consolidated Statements of Income and net OCI. OCI includes interest rate and commodity-based cash flow hedges and the related income taxes. Income or loss is recognized as the company records interest expense for hedged interest payments and as the company reaches settlement of commodity-based hedges.
Asset Retirement Obligations	Questar records an asset retirement obligation (ARO) along with an increase to the carrying value of the related property, plant and equipment when there is a legal obligation associated with the retirement of a tangible long-lived asset. Questar's AROs apply primarily to abandonment costs associated with gas and oil wells, production facilities and certain other properties. The Company has not recorded AROs on a majority of its long-lived transportation and distribution assets because the Company does not have a legal obligation to restore the area surrounding abandoned assets. The fair value of retirement costs is estimated by Company personnel based on abandonment costs of similar properties available to field operations and depreciated over the life of the related assets. Revisions to estimates result from material changes in the expected timing or amount of cash flows associated with AROs. Income or expense resulting from the settlement of ARO liabilities is included in net gain (loss) from asset sales on the Consolidated Statements of Income. The ARO liability is adjusted to present value each period through an accretion calculation using a credit-adjusted risk-free interest rate.
Business Segments	Line-of-business information is presented according to senior management's basis for evaluating performance and considering differences in the nature of products, services and regulation, among other factors.
Contingencies	A liability is recorded for a loss contingency when its occurrence is probable and its amount can be reasonably estimated. If some amount within a range of possible outcomes appears to be a better estimate than any other amount within the range, that amount is recorded. Otherwise, the minimum amount in the range is recorded. Disclosures are provided for contingencies reasonably likely to occur, which would have a material adverse effect on Questar's, Questar Gas's or Questar Pipeline's financial position, results of operations or cash flows. Some of the claims involve highly complex issues relating to liability, damages and other matters subject to substantial uncertainties and, therefore, the probability of liability or an estimate of loss cannot be reasonably determined.

Basis of Presentation of Inte19

Basis of Presentation of Interim Financial Statements (Tables)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cost of sales detail	The details of Questar's consolidated cost of sales are as follows: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Questar Gas Gas purchases $ 0.3 $ 0.1 $ 43.5 $ 96.7 $ 83.3 $ 169.6 Operator service fee 80.7 82.3 241.0 265.8 324.9 345.2 Transportation and storage 18.1 18.1 58.4 58.8 79.2 80.3 Gathering 5.7 4.5 16.7 14.2 23.5 19.4 Royalties 7.6 14.9 26.4 50.5 36.0 62.4 Storage (injection),net (42.8 ) (39.0 ) (28.6 ) (27.6 ) (2.1 ) (10.3 ) Purchased-gas account adjustment (26.4 ) (25.3 ) 0.9 (63.4 ) 18.5 (46.5 ) Other 1.2 1.2 3.7 3.6 4.9 4.9 Total Questar Gas cost of natural gas sold 44.4 56.8 362.0 398.6 568.2 625.0 Elimination of Questar Gas cost of natural gas sold - affiliated companies (98.2 ) (99.9 ) (295.4 ) (320.6 ) (398.2 ) (422.0 ) Total Questar Gas cost of natural gas sold - unaffiliated parties (53.8 ) (43.1 ) 66.6 78.0 170.0 203.0 Questar Pipeline Total Questar Pipeline cost of sales 0.6 0.6 2.3 3.0 3.3 6.4 Other cost of sales 0.6 0.2 1.3 0.6 1.6 0.7 Total cost of sales $ (52.6 ) $ (42.3 ) $ 70.2 $ 81.6 $ 174.9 $ 210.1

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Schedule of Weighted Average Number of Shares	A reconciliation of the components of basic and diluted shares used in the EPS calculation follows: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Weighted-average basic common shares outstanding 176.2 175.8 176.3 175.8 176.2 175.7 Potential number of shares issuable under the Company's LTSIP 0.1 0.3 0.2 0.3 0.2 0.3 Weighted-average diluted common shares outstanding 176.3 176.1 176.5 176.1 176.4 176.0

Accumulated Other Comprehensi21

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Details of the changes in the components of consolidated accumulated other comprehensive income (loss) (AOCI), net of income taxes, as reported in Questar's Condensed Consolidated Balance Sheets, are shown in the tables below. The tables also disclose details of income taxes related to each component of OCI. Pension and OPB Interest rate cash flow hedges Commodity cash flow hedges Long-term investment Total 3 Months Ended September 30, 2015 (in millions) AOCI at beginning of period $ (171.4 ) $ (22.3 ) $ (0.2 ) $ 0.1 $ (193.8 ) OCI before reclassifications — — 0.5 — 0.5 Reclassified from AOCI (1) 6.7 0.1 — — 6.8 Income taxes OCI before reclassifications — — (0.2 ) — (0.2 ) Reclassified from AOCI (2) (2.6 ) (0.1 ) — — (2.7 ) Total income taxes (2.6 ) (0.1 ) (0.2 ) — (2.9 ) Net other comprehensive income 4.1 — 0.3 — 4.4 AOCI at end of period $ (167.3 ) $ (22.3 ) $ 0.1 $ 0.1 $ (189.4 ) Pension and OPB Interest rate cash flow hedges Long-term investment Total 3 Months Ended September 30, 2014 (in millions) AOCI at beginning of period $ (113.7 ) $ (22.7 ) $ 0.1 $ (136.3 ) Reclassified from AOCI (1) 3.7 0.1 — 3.8 Income taxes Reclassified from AOCI (2) (1.3 ) — — (1.3 ) Total income taxes (1.3 ) — — (1.3 ) Net other comprehensive income 2.4 0.1 — 2.5 AOCI at end of period $ (111.3 ) $ (22.6 ) $ 0.1 $ (133.8 ) Pension and OPB Interest rate cash flow hedges Commodity cash flow hedges Long-term investment Total 9 Months Ended September 30, 2015 (in millions) AOCI at beginning of period $ (178.9 ) $ (22.5 ) $ — $ 0.1 $ (201.3 ) OCI before reclassifications — — 0.2 — 0.2 Reclassified from AOCI (1) 18.7 0.5 — — 19.2 Income taxes OCI before reclassifications — — (0.1 ) — (0.1 ) Reclassified from AOCI (2) (7.1 ) (0.3 ) — — (7.4 ) Total income taxes (7.1 ) (0.3 ) (0.1 ) — (7.5 ) Net other comprehensive income 11.6 0.2 0.1 — 11.9 AOCI at end of period $ (167.3 ) $ (22.3 ) $ 0.1 $ 0.1 $ (189.4 ) Pension and OPB Interest rate cash flow hedges Long-term investment Total 9 Months Ended September 30, 2014 (in millions) AOCI at beginning of period $ (119.0 ) $ (22.9 ) $ 0.1 $ (141.8 ) Reclassified from AOCI (1) 12.5 0.4 — 12.9 Income taxes Reclassified from AOCI (2) (4.8 ) (0.1 ) — (4.9 ) Total income taxes (4.8 ) (0.1 ) — (4.9 ) Net other comprehensive income 7.7 0.3 — 8.0 AOCI at end of period $ (111.3 ) $ (22.6 ) $ 0.1 $ (133.8 ) (1) Interest rate cash flow hedge amounts are included in their entirety as charges to interest expense on the Consolidated Statements of Income. (2) Income tax reclassifications related to interest rate cash flow hedge amounts are included in their entirety as credits to income taxes on the Consolidated Statements of Income.

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	9 Months Ended
	Sep. 30, 2015
Asset Retirement Obligation [Abstract]
Changes in AROs	Changes in Questar's AROs from the Condensed Consolidated Balance Sheets were as follows: 9 Months Ended September 30, 2015 2014 (in millions) AROs at beginning of year $ 69.3 $ 67.7 Accretion 2.5 2.5 Liabilities incurred 0.6 0.7 Revisions in estimated cash flows 5.7 0.4 Liabilities settled (7.1 ) (2.1 ) AROs at end of period $ 71.0 $ 69.2

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, by Balance Sheet Grouping	The following table discloses the carrying amount, estimated fair value and level within the fair value hierarchy of certain financial instruments not disclosed in other notes to Questar's financial statements in this Quarterly Report: Hierarchy Level of Fair Value Estimates Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Sept. 30, 2015 Sept. 30, 2014 Dec. 31, 2014 (in millions) Financial assets Cash and cash equivalents 1 $ — $ — $ 7.3 $ 7.3 $ 32.0 $ 32.0 Long-term investment 1 14.0 14.0 15.8 15.8 15.7 15.7 Financial liabilities Checks outstanding in excess of cash balances 1 2.8 2.8 — — — — Short-term debt 1 305.0 305.0 234.0 234.0 347.0 347.0 Long-term debt, including current portion 2 1,243.8 1,323.5 1,245.7 1,364.0 1,245.2 1,356.1
Questar Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, by Balance Sheet Grouping	The following table discloses the carrying amount, estimated fair value and level within the fair value hierarchy of certain financial instruments not disclosed in other notes to Questar Gas's financial statements in this Quarterly Report: Hierarchy Level of Fair Value Estimates Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Sept. 30, 2015 Sept. 30, 2014 Dec. 31, 2014 (in millions) Financial assets Cash and cash equivalents 1 $ — $ — $ — $ — $ 19.8 $ 19.8 Financial liabilities Checks outstanding in excess of cash balances 1 3.4 3.4 2.1 2.1 — — Notes payable to Questar 1 180.0 180.0 90.8 90.8 119.3 119.3 Long-term debt 2 534.5 588.7 534.5 602.8 534.5 607.2
Questar Pipeline [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, by Balance Sheet Grouping	The following table discloses the carrying amount, estimated fair value and level within the fair value hierarchy of certain financial instruments not disclosed in other notes to Questar Pipeline's financial statements in this Quarterly Report: Hierarchy Level of Fair Value Estimates Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Sept. 30, 2015 Sept. 30, 2014 Dec. 31, 2014 (in millions) Financial assets Cash and cash equivalents 1 $ 1.1 $ 1.1 $ 0.4 $ 0.4 $ 7.4 $ 7.4 Notes receivable from Questar 1 48.2 48.2 35.2 35.2 40.1 40.1 Financial liabilities Long-term debt, including current portion 2 458.7 484.1 458.8 505.0 458.8 495.5

Operations by Line of Busines24

Operations by Line of Business (Tables)	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Summary of operations by line of business	Following is a summary of operations by line of business: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Revenues from Unaffiliated Customers Questar Gas $ 89.3 $ 100.7 $ 605.8 $ 642.0 $ 924.7 $ 979.4 Wexpro 6.4 9.4 22.8 29.5 28.9 42.6 Questar Pipeline 45.0 47.3 138.3 143.4 185.1 190.6 Other 1.6 0.5 3.3 1.2 4.7 1.4 Total $ 142.3 $ 157.9 $ 770.2 $ 816.1 $ 1,143.4 $ 1,214.0 Revenues from Affiliated Companies Wexpro $ 80.7 $ 82.3 $ 241.1 $ 266.3 $ 325.1 $ 345.9 Questar Pipeline 17.6 17.7 54.8 54.7 73.8 76.6 Total $ 98.3 $ 100.0 $ 295.9 $ 321.0 $ 398.9 $ 422.5 Operating Income (Loss) Questar Gas $ (8.9 ) $ (9.4 ) $ 69.1 $ 60.7 $ 117.9 $ 107.3 Wexpro 40.7 47.2 124.2 141.5 166.0 187.3 Questar Pipeline 28.8 28.8 85.5 89.3 113.8 119.1 Corporate and other 1.7 2.3 5.8 2.2 (1.4 ) 2.6 Total $ 62.3 $ 68.9 $ 284.6 $ 293.7 $ 396.3 $ 416.3 Net Income (Loss) Questar Gas $ (8.8 ) $ (9.1 ) $ 32.2 $ 27.2 $ 60.2 $ 53.2 Wexpro 26.9 31.1 82.5 93.0 112.3 121.4 Questar Pipeline 15.2 14.9 44.3 46.3 58.6 62.1 Corporate and other (0.7 ) 1.7 (1.2 ) (2.5 ) (10.8 ) (4.6 ) Total $ 32.6 $ 38.6 $ 157.8 $ 164.0 $ 220.3 $ 232.1

Employee Benefits (Tables)

Employee Benefits (Tables)	9 Months Ended
	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Schedule of Defined Benefit Plans Disclosures	Components of the qualified and nonqualified net periodic pension cost are listed in the table below: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Service cost $ 3.7 $ 2.9 $ 10.5 $ 8.9 $ 13.4 $ 12.4 Interest cost 8.3 8.3 24.5 25.0 32.9 32.6 Expected return on plan assets (12.3 ) (11.4 ) (35.6 ) (32.7 ) (46.5 ) (42.2 ) Prior service cost 0.1 0.1 0.1 0.4 0.3 0.7 Recognized net actuarial loss 6.3 3.7 17.7 11.6 21.5 18.8 Net pension cost $ 6.1 $ 3.6 $ 17.2 $ 13.2 $ 21.6 $ 22.3 Net periodic postretirement benefit cost components are listed in the table below: 3 Months Ended 9 Months Ended 12 Months Ended September 30, September 30, September 30, 2015 2014 2015 2014 2015 2014 (in millions) Service cost $ 0.1 $ 0.2 $ 0.4 $ 0.5 $ 0.5 $ 0.6 Interest cost 0.8 0.9 2.6 2.9 3.5 3.8 Expected return on plan assets (0.7 ) (0.8 ) (2.3 ) (2.3 ) (3.0 ) (3.0 ) Recognized net actuarial loss (gain) 0.3 (0.1 ) 0.9 0.5 1.1 1.3 Accretion of regulatory liability 0.3 0.2 0.7 0.6 0.9 0.6 Net postretirement benefit cost $ 0.8 $ 0.4 $ 2.3 $ 2.2 $ 3.0 $ 3.3

Nature of Business (Details)

Nature of Business (Details)	9 Months Ended
	Sep. 30, 2015lines_of_business
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of principal complementary lines of business	3

Basis of Presentation of Inte27

Basis of Presentation of Interim Financial Statements (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)customers	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Mar. 31, 2015USD ($)
Cost of Sales [Abstract]
Other cost of sales	$ 0.6	$ 0.2	$ 1.3	$ 0.6	$ 1.6	$ 0.7
Total cost of sales	(52.6)	(42.3)	$ 70.2	81.6	174.9	210.1
Questar Gas [Member]
Payments for Questar Gas Acquisition							$ 11.4
Additional Customers from Questar Gas Acquisition | customers			6,500
Cost of Sales [Abstract]
Gas purchases	0.3	0.1	$ 43.5	96.7	83.3	169.6
Operator service fee	80.7	82.3	241	265.8	324.9	345.2
Transportation and storage	18.1	18.1	58.4	58.8	79.2	80.3
Gathering	5.7	4.5	16.7	14.2	23.5	19.4
Royalties	7.6	14.9	26.4	50.5	36	62.4
Storage (injection),net	(42.8)	(39)	(28.6)	(27.6)	(2.1)	(10.3)
Purchased-gas account adjustment	(26.4)	(25.3)	0.9	(63.4)	18.5	(46.5)
Other	1.2	1.2	3.7	3.6	4.9	4.9
Total Questar Gas cost of natural gas sold	44.4	56.8	362	398.6	568.2	625
Elimination of Questar Gas cost of natural gas sold - affiliated companies	(98.2)	(99.9)	(295.4)	(320.6)	(398.2)	(422)
Total Questar Gas cost of natural gas sold - unaffiliated parties	$ (53.8)	(43.1)	$ 66.6	78	$ 170	203
Questar Pipeline [Member]
Ownership percentage in unconsolidated affiliate (in hundredths)	50.00%		50.00%		50.00%
Cost of Sales [Abstract]
Total Questar Pipeline cost of sales	$ 0.6	$ 0.6	$ 2.3	$ 3	$ 3.3	$ 6.4

Earnings Per Share (Details)

Earnings Per Share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Weighted-average basic common shares outstanding (in shares)	176.2	175.8	176.3	175.8	176.2	175.7
Potential number of shares issuable under the Company's LTSIP (in shares)	0.1	0.3	0.2	0.3	0.2	0.3
Weighted-average diluted common shares outstanding (in shares)	176.3	176.1	176.5	176.1	176.4	176

Accumulated Other Comprehensi29

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
AOCI at beginning of period		$ (193.8)	$ (136.3)	$ (201.3)	$ (141.8)	$ (133.8)
OCI before reclassifications		0.5		0.2
Reclassified from AOCI	[1]	6.8	3.8	19.2	12.9
Income taxes
OCI before reclassifications		(0.2)		(0.1)
Reclassified from AOCI	[2]	(2.7)	(1.3)	(7.4)	(4.9)
Total income taxes		(2.9)	(1.3)	(7.5)	(4.9)	34.3	$ (60.2)
Net other comprehensive income (loss)		4.4	2.5	11.9	8	(55.6)	96.9
AOCI at end of period		(189.4)	(133.8)	(189.4)	(133.8)	(189.4)	(133.8)
Reclassification Adjustment out of Accumulated Other Comphrensive Income [Abstract]
Income tax benefit		16.2	17.5	86.4	90.1	122.2	132
Pension and OPRB
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
AOCI at beginning of period		(171.4)	(113.7)	(178.9)	(119)	(111.3)
OCI before reclassifications		0		0
Reclassified from AOCI	[1]	6.7	3.7	18.7	12.5
Income taxes
OCI before reclassifications		0		0
Reclassified from AOCI	[2]	(2.6)	(1.3)	(7.1)	(4.8)
Total income taxes		(2.6)	(1.3)	(7.1)	(4.8)
Net other comprehensive income (loss)		4.1	2.4	11.6	7.7
AOCI at end of period		(167.3)	(111.3)	(167.3)	(111.3)	(167.3)	(111.3)
Long-term invest.
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
AOCI at beginning of period		0.1	0.1	0.1	0.1	0.1
OCI before reclassifications		0		0
Reclassified from AOCI	[1]	0	0	0	0
Income taxes
OCI before reclassifications		0		0
Reclassified from AOCI	[2]	0	0	0	0
Total income taxes		0	0	0	0
Net other comprehensive income (loss)		0	0	0	0
AOCI at end of period		0.1	0.1	0.1	0.1	0.1	0.1
Questar Pipeline [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
AOCI at beginning of period				(22.5)		(22.6)
Income taxes
Total income taxes		(0.3)	0	(0.4)	(0.1)	(0.4)	(0.2)
Net other comprehensive income (loss)		0.3	0.1	0.3	0.3	0.4	0.3
AOCI at end of period		(22.2)	(22.6)	(22.2)	(22.6)	(22.2)	(22.6)
Reclassification Adjustment out of Accumulated Other Comphrensive Income [Abstract]
Income tax benefit		8	8.6	24.8	26.8	33.6	36
Questar Pipeline [Member] | Interest rate cash flow hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
AOCI at beginning of period		(22.3)	(22.7)	(22.5)	(22.9)	(22.6)
OCI before reclassifications		0		0
Reclassified from AOCI	[1]	0.1	0.1	0.5	0.4
Income taxes
OCI before reclassifications		0		0
Reclassified from AOCI	[2]	(0.1)	0	(0.3)	(0.1)
Total income taxes		(0.1)	0	(0.3)	(0.1)
Net other comprehensive income (loss)		0	0.1	0.2	0.3
AOCI at end of period		(22.3)	(22.6)	(22.3)	(22.6)	(22.3)	(22.6)
Questar Pipeline [Member] | Interest rate cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comphrensive Income [Abstract]
Interest (expense)		0.1	0.1	0.5	0.4	0.6	0.5
Income tax benefit		(0.1)	$ 0	(0.3)	$ (0.1)	(0.3)	$ (0.2)
Questar Pipeline [Member] | Commodity cash flow hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
AOCI at beginning of period		(0.2)		0
OCI before reclassifications		0.5		0.2
Reclassified from AOCI	[1]	0		0
Income taxes
OCI before reclassifications		(0.2)		(0.1)
Reclassified from AOCI	[2]	0		0
Total income taxes		(0.2)		(0.1)
Net other comprehensive income (loss)		0.3		0.1
AOCI at end of period		$ 0.1		$ 0.1		$ 0.1
[1]	Interest rate cash flow hedge amounts are included in their entirety as charges to interest expense on the Consolidated Statements of Income.
[2]	Income tax reclassifications related to interest rate cash flow hedge amounts are included in their entirety as credits to income taxes on the Consolidated Statements of Income.

Asset Retirement Obligations (

Asset Retirement Obligations (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
AROs at beginning of year	$ 69.3	$ 67.7
Accretion	2.5	2.5
Liabilities incurred	0.6	0.7
Revisions in estimated cash flows	5.7	0.4
Liabilities settled	(7.1)	(2.1)
AROs at end of period	$ 71	$ 69.2

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Carrying Amount [Member]
Financial assets [Abstract]
Cash and cash equivalents	$ 0	$ 32	$ 7.3
Long-term investment	14	15.7	15.8
Financial liabilities [Abstract]
Checks outstanding in excess of cash balances	2.8	0	0
Short-term debt	305	347	234
Long-term debt, including current portion	1,243.8	1,245.2	1,245.7
Estimated Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	32	7.3
Financial liabilities [Abstract]
Checks outstanding in excess of cash balances	2.8	0	0
Short-term debt	305	347	234
Estimated Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]
Financial liabilities [Abstract]
Long-term debt, including current portion	1,323.5	1,356.1	1,364
Estimated Fair Value [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets [Abstract]
Long-term investment	14	15.7	15.8
Questar Gas [Member] | Carrying Amount [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	19.8	0
Financial liabilities [Abstract]
Checks outstanding in excess of cash balances	3.4	0	2.1
Notes payable to Questar	180	119.3	90.8
Long-term debt, including current portion	534.5	534.5	534.5
Questar Gas [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	19.8	0
Financial liabilities [Abstract]
Checks outstanding in excess of cash balances	3.4	0	2.1
Notes payable to Questar	180	119.3	90.8
Questar Gas [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]
Financial liabilities [Abstract]
Long-term debt, including current portion	588.7	607.2	602.8
Questar Pipeline [Member] | Carrying Amount [Member]
Financial assets [Abstract]
Cash and cash equivalents	1.1	7.4	0.4
Notes receivable from Questar	48.2	40.1	35.2
Financial liabilities [Abstract]
Long-term debt, including current portion	458.7	458.8	458.8
Questar Pipeline [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets [Abstract]
Cash and cash equivalents	1.1	7.4	0.4
Notes receivable from Questar	48.2	40.1	35.2
Questar Pipeline [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]
Financial liabilities [Abstract]
Long-term debt, including current portion	$ 484.1	$ 495.5	$ 505

Derivatives and Hedging (Detail

Derivatives and Hedging (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2011	Sep. 30, 2015	Dec. 31, 2011	Dec. 31, 2014	Sep. 30, 2014
Derivative [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net		$ 200,000		$ 0	$ 0
Cash Flow Hedging [Member] | Questar Pipeline [Member] | Forward Starting Interest Rate Swaps Terminating Q4 2011 [Member]
Derivative [Line Items]
Notional amount	$ 150,000,000		$ 150,000,000
Debt Instrument, Face Amount	180,000,000		$ 180,000,000
Interest payment for terminated derivative instrument	$ 37,300,000
Life of long-term debt associated with cash flow hedges			30 years
Date Through Which Reclassifications Into Earnings From AOCI Will Take Place		2,041
Pre-tax net losses expected to be reclassified from AOCI to Consolidated statement of income		$ 500,000
Reclassification from accumulated OCI to income, time to transfer		12 months

Operations by Line of Busines33

Operations by Line of Business (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)lines_of_business	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)
Segment Reporting Information [Line Items]
Number of principal complementary lines of business | lines_of_business			3
Revenues by Line of Business	$ 142.3	$ 157.9	$ 770.2	$ 816.1	$ 1,143.4	$ 1,214
Operating Income (Loss)	62.3	68.9	284.6	293.7	396.3	416.3
Net Income (Loss)	32.6	38.6	157.8	164	220.3	232.1
Questar Gas [Member]
Segment Reporting Information [Line Items]
Revenues by Line of Business	89.3	100.7	605.8	642	924.7	979.4
Operating Income (Loss)	(8.9)	(9.4)	69.1	60.7	117.9	107.3
Net Income (Loss)	(8.8)	(9.1)	32.2	27.2	60.2	53.2
Wexpro [Member]
Segment Reporting Information [Line Items]
Revenues by Line of Business	6.4	9.4	22.8	29.5	28.9	42.6
Operating Income (Loss)	40.7	47.2	124.2	141.5	166	187.3
Net Income (Loss)	26.9	31.1	82.5	93	112.3	121.4
Questar Pipeline [Member]
Segment Reporting Information [Line Items]
Revenues by Line of Business	45	47.3	138.3	143.4	185.1	190.6
Operating Income (Loss)	28.8	28.8	85.5	89.3	113.8	119.1
Net Income (Loss)	15.2	14.9	44.3	46.3	58.6	62.1
Questar Corp and Other [Member]
Segment Reporting Information [Line Items]
Revenues by Line of Business	1.6	0.5	3.3	1.2	4.7	1.4
Operating Income (Loss)	1.7	2.3	5.8	2.2	(1.4)	2.6
Net Income (Loss)	(0.7)	1.7	(1.2)	(2.5)	(10.8)	(4.6)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues by Line of Business	98.3	100	295.9	321	398.9	422.5
Intersegment Eliminations [Member] | Wexpro [Member]
Segment Reporting Information [Line Items]
Revenues by Line of Business	80.7	82.3	241.1	266.3	325.1	345.9
Intersegment Eliminations [Member] | Questar Pipeline [Member]
Segment Reporting Information [Line Items]
Revenues by Line of Business	$ 17.6	$ 17.7	$ 54.8	$ 54.7	$ 73.8	$ 76.6

Employee Benefits (Details)

Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Qualified and nonqualified pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3.7	$ 2.9	$ 10.5	$ 8.9	$ 13.4	$ 12.4
Interest cost	8.3	8.3	24.5	25	32.9	32.6
Expected return on plan assets	(12.3)	(11.4)	(35.6)	(32.7)	(46.5)	(42.2)
Prior service cost	0.1	0.1	0.1	0.4	0.3	0.7
Recognized net actuarial loss	6.3	3.7	17.7	11.6	21.5	18.8
Net benefit cost	6.1	3.6	17.2	13.2	21.6	22.3
Estimated qualified pension plan cost for current fiscal year	19		19		19
Estimated nonqualified pension plan cost for current fiscal year	3.9		3.9		3.9
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year			69
Postretirement benefits plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1	0.2	0.4	0.5	0.5	0.6
Interest cost	0.8	0.9	2.6	2.9	3.5	3.8
Expected return on plan assets	(0.7)	(0.8)	(2.3)	(2.3)	(3)	(3)
Recognized net actuarial loss (gain)	0.3	(0.1)	0.9	0.5	1.1	1.3
Accretion of regulatory liability	0.3	0.2	0.7	0.6	0.9	0.6
Net benefit cost	0.8	$ 0.4	2.3	$ 2.2	3	$ 3.3
Estimated postretirement benefits cost for current fiscal year, before accretion of regulatory liability	$ 2.1		$ 2.1		$ 2.1

Contingencies (Details)

Contingencies (Details) $ in Millions	Sep. 30, 2015USD ($)
Wexpro [Member]
Loss Contingencies [Line Items]
Overriding royalty interest	4.00%
Loss Contingency, Range of Possible Loss, Maximum	$ 14.1
Unaffiliated Entity [Member]
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Maximum	$ 16.2

Asset Impairments (Details)

Asset Impairments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment [Line Items]
Pre-tax asset impairment charge	$ 0	$ 0	$ 0.1	$ 2	$ 0.1	$ 2
Net (gain) from asset sales	0.2	1.5	$ 1.6	$ 1.6	$ 1.2	$ 1.3
Wexpro [Member] | Wexpro Brady Field [Member]
Property, Plant and Equipment [Line Items]
Pre-tax asset impairment charge		$ 2
Net (gain) from asset sales	$ 1.4