Questar Gas 10-Q 30 Apr 14 2014 Q1 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	3 Months Ended
	Mar. 31, 2014
Entity Information [Line Items]	'
Entity Registrant Name	'QUESTAR CORP
Entity Central Index Key	'0000751652
Current Fiscal Year End Date	'--12-31
Entity Filer Category	'Large Accelerated Filer
Document Type	'10-Q
Document Period End Date	31-Mar-14
Document Fiscal Year Focus	'2014
Document Fiscal Period Focus	'Q1
Amendment Flag	'false
Entity Common Stock, Shares Outstanding	175,145,913
Questar Gas [Member]	'
Entity Information [Line Items]	'
Entity Registrant Name	'QUESTAR GAS CO
Entity Central Index Key	'0000068589
Current Fiscal Year End Date	'--12-31
Entity Filer Category	'Non-accelerated Filer
Document Type	'10-Q
Document Period End Date	31-Mar-14
Document Fiscal Year Focus	'2014
Document Fiscal Period Focus	'Q1
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	'0000764044
Current Fiscal Year End Date	'--12-31
Entity Filer Category	'Non-accelerated Filer
Document Type	'10-Q
Document Period End Date	31-Mar-14
Document Fiscal Year Focus	'2014
Document Fiscal Period Focus	'Q1
Amendment Flag	'false
Entity Common Stock, Shares Outstanding	6,550,843

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (USD $)	3 Months Ended		12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
REVENUES	'	'	'	'
Questar Gas / Revenues from unaffiliated customers	$396.30	$418.30	$963.20	$912
Wexpro	12.3	10.3	47.1	37.2
Questar Pipeline / Revenues from unaffiliated customers	48	48.3	189.2	200.9
Other	0.3	0	0.5	0
Total Revenues	456.9	476.9	1,200	1,150.10
OPERATING EXPENSES	'	'	'	'
Cost of sales (excluding operating expenses shown separately)	148.2	199.7	234.4	239.3
Operating and maintenance	55.7	48.2	181.8	172.3
General and administrative	31.5	33.8	118.7	125.5
Retirement incentive	0	0	0	4.9
Production and other taxes	17.9	15.3	60	48.9
Depreciation, depletion and amortization	55.3	48.5	201.6	185.9
Asset impairment	0	0	80.6	0
Total Operating Expenses	308.6	345.5	877.1	776.8
Net gain (loss) from asset sales	0	0	-0.2	2.9
OPERATING INCOME	148.3	131.4	322.7	376.2
Interest and other income	1.8	3	8.7	8.6
Income from unconsolidated affiliate	0.9	0.9	3.7	3.7
Interest expense	-15.8	-14.5	-58.2	-57.7
INCOME BEFORE INCOME TAXES	135.2	120.8	276.9	330.8
Income taxes	-50.1	-47.9	-103.5	-121.1
NET INCOME	85.1	72.9	173.4	209.7
Earnings Per Common Share	'	'	'	'
Basic	$0.48	$0.42	$0.98	$1.20
Diluted	$0.48	$0.41	$0.98	$1.19
Weighted-average common shares outstanding	'	'	'	'
Used in basic calculation	175.7	175.3	175.6	175.6
Used in diluted calculation	176.1	176.1	176.1	176.5
Dividends per common share	$0.18	$0.17	$0.72	$0.67
Questar Gas [Member]	'	'	'	'
REVENUES	'	'	'	'
Questar Gas / Revenues from unaffiliated customers	396.3	418.3	963.2	912
Revenues from affiliated company	0	0.3	0.3	2
Total Revenues	396.3	418.6	963.5	914
OPERATING EXPENSES	'	'	'	'
Cost of natural gas sold (excluding operating expenses shown separately)	254.6	290.6	614.6	587.7
Operating and maintenance	39.8	33.7	119.2	111.8
General and administrative	13.8	12.7	53.6	52.2
Retirement incentive	0	0	0	2.4
Depreciation and amortization	13.2	12.1	50.8	47.5
Other taxes	5.1	5.2	17.9	17
Total Operating Expenses	326.5	354.3	856.1	818.6
OPERATING INCOME	69.8	64.3	107.4	95.4
Interest and other income	1.3	1.2	5.2	5.5
Interest expense	-7.1	-5.8	-23.6	-23.1
INCOME BEFORE INCOME TAXES	64	59.7	89	77.8
Income taxes	-24.4	-22.7	-33.6	-28.6
NET INCOME	39.6	37	55.4	49.2
Questar Pipeline [Member]	'	'	'	'
REVENUES	'	'	'	'
Questar Pipeline / Revenues from unaffiliated customers	48	48.3	189.2	200.9
Revenues from affiliated companies	19.3	19.5	76.5	75.4
Total Revenues	67.3	67.8	265.7	276.3
OPERATING EXPENSES	'	'	'	'
Operating and maintenance	8.1	7.4	33.2	34
General and administrative	11.5	12.4	45.8	50.3
Retirement incentive	0	0	0	0.9
Depreciation and amortization	13.6	14.1	55	54.9
Asset impairment	0	0	80.6	0
Other taxes	2.3	2.5	9.1	9.1
Cost of sales (excluding operating expenses shown separately)	1.7	1.2	6.6	7.4
Total Operating Expenses	37.2	37.6	230.3	156.6
Net gain (loss) from asset sales	0	0	0	2.7
OPERATING INCOME	30.1	30.2	35.4	122.4
Interest and other income	0.3	0.3	1.8	0.9
Income from unconsolidated affiliate	0.9	0.9	3.7	3.7
Interest expense	-6.5	-6.5	-25.8	-26.2
INCOME BEFORE INCOME TAXES	24.8	24.9	15.1	100.8
Income taxes	-9.1	-9.1	-7	-36.9
NET INCOME	$15.70	$15.80	$8.10	$63.90

CONDENSED_CONSOLIDATED_STATEME

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Net income	$85.10	$72.90	$173.40	$209.70
Other comprehensive income (loss):	'	'	'	'
Pension and other postretirement benefits	4.3	7.8	165.3	-31.8
Interest rate cash flow hedges	0.2	0.2	0.5	0.5
Change in fair value of long-term investment	0	0	-0.1	0.1
Income taxes	-1.8	-3	-63.5	11.9
Net other comprehensive income (loss)	2.7	5	102.2	-19.3
COMPREHENSIVE INCOME	87.8	77.9	275.6	190.4
Questar Pipeline [Member]	'	'	'	'
Net income	15.7	15.8	8.1	63.9
Other comprehensive income (loss):	'	'	'	'
Interest rate cash flow hedges	0.2	0.2	0.5	0.5
Income taxes	-0.1	-0.1	-0.2	-0.2
Net other comprehensive income (loss)	0.1	0.1	0.3	0.3
COMPREHENSIVE INCOME	$15.80	$15.90	$8.40	$64.20

CONDENSED_CONSOLIDATED_BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Millions, unless otherwise specified
Current Assets	'	'	'
Cash and cash equivalents	$5.60	$16	$7.20
Accounts receivable, net	130.6	123.8	141.2
Unbilled gas accounts receivable	56.3	93.4	50.5
Gas stored underground	6.9	40	9.8
Materials and supplies	25	23.7	30
Current regulatory assets	29.8	35.8	31.3
Prepaid expenses and other	7.5	9.5	6.8
Deferred income taxes - current	14.5	9.7	17.2
Total Current Assets	276.2	351.9	294
Property, Plant and Equipment	5,723.50	5,674.70	5,399.40
Accumulated depreciation, depletion and amortization	-2,121.60	-2,071.70	-2,011
Net Property, Plant and Equipment	3,601.90	3,603	3,388.40
Investment in unconsolidated affiliate	25.2	25.6	26.1
Noncurrent regulatory assets	19.3	20.5	20.4
Other noncurrent assets	51.8	53.3	47.8
TOTAL ASSETS	3,974.40	4,054.30	3,776.70
Current Liabilities	'	'	'
Short-term debt	157	276	202
Accounts payable and accrued expenses	229.9	264.8	222.8
Current regulatory liabilities	17.2	14.1	36.8
Current portion of long-term debt and capital lease obligation	0.9	0.9	2.8
Total Current Liabilities	405	555.8	464.4
Long-term debt and capital lease obligation, less current portion	1,284.70	1,285.50	1,137.60
Deferred income taxes	712.6	707.2	636.1
Asset retirement obligations	68.6	67.7	61.2
Defined benefit pension plan and other postretirement benefits	108.5	113.2	271.3
Noncurrent regulatory liabilities	63.2	61.2	56.5
Customer contributions in aid of construction	32	29.1	23.8
Other noncurrent liabilities	43.6	35.8	39.7
COMMON SHAREHOLDERS' EQUITY	'	'	'
Common stock	465.7	464.5	444.8
Retained earnings	929.6	876.1	882.6
Accumulated other comprehensive (loss)	-139.1	-141.8	-241.3
Total Common Shareholders' Equity	1,256.20	1,198.80	1,086.10
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	3,974.40	4,054.30	3,776.70
Questar Gas [Member]	'	'	'
Current Assets	'	'	'
Cash and cash equivalents	1.4	8.8	2.8
Notes receivable from Questar	30.6	0	0
Accounts receivable, net	102.6	88.9	103.7
Unbilled gas accounts receivable	56.3	93.4	50.4
Accounts receivable from affiliates	31.3	30.4	32.8
Gas stored underground	6.2	39.2	9.6
Materials and supplies	13.2	12.1	14.4
Current regulatory assets	24	30.2	26.1
Prepaid expenses and other	2.4	3	2.2
Deferred income taxes - current	2.9	2.9	5.7
Total Current Assets	270.9	308.9	247.7
Property, Plant and Equipment	2,230	2,203	2,062.80
Accumulated depreciation, depletion and amortization	-754.3	-745.2	-724
Net Property, Plant and Equipment	1,475.70	1,457.80	1,338.80
Noncurrent regulatory assets	15.4	16.1	15.7
Goodwill	5.6	5.6	5.6
Other noncurrent assets	3.9	4	3.1
TOTAL ASSETS	1,771.50	1,792.40	1,610.90
Current Liabilities	'	'	'
Notes payable to Questar	0	17.7	132.3
Accounts payable and accrued expenses	111.3	139.2	109.9
Accounts payable to affiliates	65.6	67.8	51.1
Customer advances	7.2	19.8	7.2
Current regulatory liabilities	15.2	11.1	35.6
Current portion of long-term debt and capital lease obligation	0	0	2
Total Current Liabilities	199.3	255.6	338.1
Long-term debt and capital lease obligation, less current portion	534.5	534.5	384.5
Deferred income taxes	340.6	340.7	316.5
Noncurrent regulatory liabilities	54.8	53	48.6
Customer contributions in aid of construction	32	29.1	23.8
Other noncurrent liabilities	3.1	3.2	3.3
COMMON SHAREHOLDERS' EQUITY	'	'	'
Common stock	23	23	23
Additional paid-in capital	264.2	263.9	172.9
Retained earnings	320	289.4	300.2
Total Common Shareholders' Equity	607.2	576.3	496.1
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	1,771.50	1,792.40	1,610.90
Questar Pipeline [Member]	'	'	'
Current Assets	'	'	'
Cash and cash equivalents	4.9	2.7	5.4
Notes receivable from Questar	46.6	29.4	33.1
Accounts receivable, net	17.5	18.5	18.6
Accounts receivable from affiliates	33.8	36.6	34
Materials and supplies	8.2	8.1	10.9
Current regulatory assets	5.8	5.6	5.2
Prepaid expenses and other	2.8	4.4	3.3
Deferred income taxes - current	1.8	1.8	1.6
Total Current Assets	121.4	107.1	112.1
Property, Plant and Equipment	1,782.80	1,774.30	1,852.70
Accumulated depreciation, depletion and amortization	-640.6	-627.2	-642.7
Net Property, Plant and Equipment	1,142.20	1,147.10	1,210
Investment in unconsolidated affiliate	25.2	25.6	26.1
Goodwill	4.2	4.2	4.2
Noncurrent regulatory and other assets	7.1	7.7	8.7
TOTAL ASSETS	1,300.10	1,291.70	1,361.10
Current Liabilities	'	'	'
Accounts payable and accrued expenses	38.7	25.6	31.5
Accounts payable to affiliates	3.4	9.4	3.4
Current regulatory liabilities	2	3	1.2
Total Current Liabilities	44.1	38	36.1
Long-term debt and capital lease obligation, less current portion	458.8	458.9	458.9
Deferred income taxes	228.6	228.6	245.8
Noncurrent regulatory and other liabilities	15.9	13.9	14
COMMON SHAREHOLDERS' EQUITY	'	'	'
Common stock	6.6	6.6	6.6
Additional paid-in capital	350.1	349.5	348.1
Retained earnings	218.8	219.1	274.7
Accumulated other comprehensive (loss)	-22.8	-22.9	-23.1
Total Common Shareholders' Equity	552.7	552.3	606.3
TOTAL LIABILITIES AND COMMON SHAREHOLDERS' EQUITY	$1,300.10	$1,291.70	$1,361.10

CONDENSED_CONSOLIDATED_STATEME1

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
OPERATING ACTIVITIES	'	'
Net income	$85.10	$72.90
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation, depletion and amortization	57.2	50.2
Deferred income taxes	-1.2	25.4
Asset impairment	0	0
Share-based compensation	3.2	3.1
(Income) from unconsolidated affiliate	-0.9	-0.9
Distributions from unconsolidated affiliate and other	1.6	1.5
Changes in operating assets and liabilities	67.9	53.8
Net Cash Provided By Operating Activities	212.9	206
INVESTING ACTIVITIES	'	'
Property, plant and equipment	-69.7	-84
Cash used in disposition of assets	-0.9	-0.5
Proceeds from disposition of assets	0	0.1
Net Cash Used In Investing Activities	-70.6	-84.4
FINANCING ACTIVITIES	'	'
Common stock issued	0.5	1.8
Common stock repurchased	-2.8	-3.5
Change in short-term debt	-119	-61
Long-term debt and capital lease obligation repaid	-0.3	-40.1
Dividends paid	-31.6	-29.8
Tax benefits from share-based compensation	0.5	1.4
Net Cash Provided By (Used In) Financing Activities	-152.7	-131.2
Change in cash and cash equivalents	-10.4	-9.6
Beginning cash and cash equivalents	16	16.8
Ending cash and cash equivalents	5.6	7.2
Questar Gas [Member]	'	'
OPERATING ACTIVITIES	'	'
Net income	39.6	37
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	14.6	13.4
Deferred income taxes	-0.1	10.7
Share-based compensation	0.3	0.4
Changes in operating assets and liabilities	45.3	44
Net Cash Provided By Operating Activities	99.7	105.5
INVESTING ACTIVITIES	'	'
Property, plant and equipment	-48.9	-31.7
Cash used in disposition of assets	-0.9	-0.4
Affiliated-company property, plant and equipment transfers	0	10.7
Net Cash Used In Investing Activities	-49.8	-21.4
FINANCING ACTIVITIES	'	'
Change in notes receivable from Questar	-30.6	0
Change in notes payable to Questar	-17.7	-33.8
Long-term debt and capital lease obligation repaid	0	-40
Dividends paid	-9	-8.9
Net Cash Provided By (Used In) Financing Activities	-57.3	-82.7
Change in cash and cash equivalents	-7.4	1.4
Beginning cash and cash equivalents	8.8	1.4
Ending cash and cash equivalents	1.4	2.8
Questar Pipeline [Member]	'	'
OPERATING ACTIVITIES	'	'
Net income	15.7	15.8
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization	14.1	14.7
Deferred income taxes	-0.1	3.2
Asset impairment	0	0
Share-based compensation	0.6	0.7
(Income) from unconsolidated affiliate	-0.9	-0.9
Distributions from unconsolidated affiliate and other	1.5	1.5
Changes in operating assets and liabilities	13	-1.4
Net Cash Provided By Operating Activities	43.9	33.6
INVESTING ACTIVITIES	'	'
Property, plant and equipment	-8.5	-14.1
Cash used in disposition of assets	0	-0.1
Affiliated-company property, plant and equipment transfers	0	-10.7
Net Cash Used In Investing Activities	-8.5	-24.9
FINANCING ACTIVITIES	'	'
Change in notes receivable from Questar	-17.2	5.6
Dividends paid	-16	-16
Net Cash Provided By (Used In) Financing Activities	-33.2	-10.4
Change in cash and cash equivalents	2.2	-1.7
Beginning cash and cash equivalents	2.7	7.1
Ending cash and cash equivalents	$4.90	$5.40

Nature_of_Business_Notes

Nature of Business (Notes)	3 Months Ended
	Mar. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Nature of Business	'
	Note 1 - 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_Inter

Basis of Presentation of Interim Financial Statements (Notes)	3 Months Ended
	Mar. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of Presentation of Interim Financial Statements	'
	Note 2 - 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, 2013.
	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 and 12 months ended March 31, 2014, are not necessarily indicative of the results that may be expected for the year ending December 31, 2014.
	Certain reclassifications were made to prior year information to conform to the current year presentation. Questar and Questar Gas reclassified amounts received from customers for the cost of plant removal from accumulated depreciation to a regulatory liability for the prior year. In addition, there were reclassifications on the Questar Condensed Consolidated Statements of Comprehensive Income and Condensed Consolidated Balance Sheets to reflect revised accounting for reclassifications out of accumulated other comprehensive loss related to the Company's pension and other postretirement benefit plans. These reclassifications did not impact net income or cash flows. The Company does not believe these changes are material to prior year financial statements.
	Questar uses the equity method to account for its investment in an unconsolidated affiliate where it does not have control, but has significant influence. White River Hub, LLC is a limited liability company and FERC-regulated transporter of natural gas. Questar Pipeline owns 50% of White River Hub, LLC and is the operator. Generally, the investment in White River Hub, LLC on the Company's balance sheets equals the Company's proportionate share of equity reported by White River Hub, LLC. The investment is assessed for possible impairment when events indicate that the fair value of the investment may be below the Company'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.
	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. 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						12 Months Ended
		March 31,						March 31,
		2014			2013			2014			2013
		(in millions)
	Questar Gas
	Gas purchases	$	92.7		$	103.3		$	176		$	146
	Operator service fee	89.1			72.8			310.9			281.1
	Transportation and storage	22.1			22			80.2			81
	Gathering	4.9			4.6			19.1			19
	Royalties	17.3			11.1			50.5			32.9
	Storage withdrawal, net	33			28.8			3.4			3.3
	Purchased-gas account adjustment	(5.6		)	46.7			(30.3		)	19.4
	Other	1.1			1.3			4.8			5
	Total Questar Gas cost of natural gas sold	254.6			290.6			614.6			587.7
	Elimination of Questar Gas cost of natural gas sold - affiliated parties	(108.2		)	(92.1		)	(387.0		)	(355.8		)
	Total Questar Gas cost of natural gas sold - unaffiliated parties	146.4			198.5			227.6			231.9
	Questar Pipeline
	Total Questar Pipeline cost of sales	1.7			1.2			6.6			7.4
	Other cost of sales	0.1			—			0.2			—
	Total cost of sales	$	148.2		$	199.7		$	234.4		$	239.3

Earnings_Per_Share_Notes

Earnings Per Share (Notes)	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	Note 3 - 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). 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 dividends 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 are participating securities for the computation of basic earnings per share. The application of the two-class method had an insignificant impact on the calculation of both basic and diluted EPS. A reconciliation of the components of basic and diluted shares used in the EPS calculation follows:
		3 Months Ended		12 Months Ended
		March 31,		March 31,
		2014	2013	2014	2013
		(in millions)
	Weighted-average basic common shares outstanding	175.7	175.3	175.6	175.6
	Potential number of shares issuable under the Company's LTSIP	0.4	0.8	0.5	0.9
	Weighted-average diluted common shares outstanding	176.1	176.1	176.1	176.5

Other_Comprehensive_Income_Not

Other Comprehensive Income (Notes)	3 Months Ended
	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]	'
Other Comprehensive Income	'
	Note 4 - 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 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 (OPRB) costs are accrued, as the Company records interest expense for hedged interest payments and when the long-term investment is sold or otherwise realized.
	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 OPRB			Interest rate cash flow hedges			Long-term invest.			Total			Pension and OPRB			Interest rate cash flow hedges			Long-term invest.		Total
		3 Months Ended												3 Months Ended
		March 31, 2014												March 31, 2013
		(in millions)
	AOCI at beginning of period	$	(119.0	)	$	(22.9	)	$	0.1		$	(141.8	)	$	(223.2	)	$	(23.2	)	$	0.1	$	(246.3	)
	Reclassified from AOCI(1)	4.3			0.2			—			4.5			7.8			0.2			—		8
	Income taxes
	Reclassified from AOCI(2)	(1.7		)	(0.1		)	—			(1.8		)	(2.9		)	(0.1		)	—		(3.0		)
	Net other comprehensive income	2.6			0.1			—			2.7			4.9			0.1			—		5
	AOCI at March 31,	$	(116.4	)	$	(22.8	)	$	0.1		$	(139.1	)	$	(218.3	)	$	(23.1	)	$	0.1	$	(241.3	)
		Pension and OPRB			Interest rate cash flow hedges			Long-term invest.			Total
		12 Months Ended
		March 31, 2014
		(in millions)
	AOCI at beginning of period	$	(218.3	)	$	(23.1	)	$	0.1		$	(241.3	)
	OCI before reclassifications	135.8			—			(0.1		)	135.7
	Reclassified from AOCI(1)	29.5			0.5			—			30
	Income taxes
	OCI before reclassifications	(51.9		)	—			0.1			(51.8		)
	Reclassified from AOCI(2)	(11.5		)	(0.2		)	—			(11.7		)
	Total income taxes	(63.4		)	(0.2		)	0.1			(63.5		)
	Net other comprehensive income	101.9			0.3			—			102.2
	AOCI at March 31,	$	(116.4	)	$	(22.8	)	$	0.1		$	(139.1	)
	(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.
	Pension and other postretirement benefit AOCI reclassifications are included in the computation of net periodic pension and postretirement benefit costs. See Note 10 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 cash flow hedges and the related income taxes. Income or loss is recognized as the company records interest expense for hedged interest payments. Disclosures above regarding interest rate cash flow hedges, including related income taxes and income statement reclassification effects, apply to Questar Pipeline.

Asset_Retirement_Obligations_N

Asset Retirement Obligations (Notes)	3 Months Ended
	Mar. 31, 2014
Asset Retirement Obligation [Abstract]	'
Asset Retirement Obligations	'
	Note 5 - 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:
		3 Months Ended
		March 31,
		2014			2013
		(in millions)
	AROs at beginning of year	$	67.7		$	67.2
	Accretion	0.8			0.8
	Liabilities incurred	0.4			0.4
	Revisions in estimated cash flows	0.4			(6.8		)
	Liabilities settled	(0.7		)	(0.4		)
	AROs at March 31,	$	68.6		$	61.2
	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 Agreement 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)	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Note 6 - 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. The Company had no assets or liabilities measured using Level 3 inputs at March 31, 2014, March 31, 2013 or December 31, 2013. Fair value accounting standards also apply to certain nonfinancial assets and liabilities that are measured at fair value on a nonrecurring basis. Questar did not have any such assets or liabilities at March 31, 2014, March 31, 2013 or December 31, 2013.
	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 on Form 10-Q:
		Hierarchy Level of Fair Value Estimates	Carrying		Estimated		Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value		Amount		Fair Value
			Mar. 31, 2014				Mar. 31, 2013				Dec. 31, 2013
			(in millions)
	Financial assets
	Cash and cash equivalents	1	$	5.6	$	5.6	$	7.2	$	7.2	$	16	$	16
	Long-term investment	1	15.3		15.3		16.1		16.1		17.3		17.3
	Financial liabilities
	Short-term debt	1	157		157		202		202		276		276
	Long-term debt, including current portion	2	1,246.60		1,357.50		1,100.50		1,260.10		1,247.10		1,310.80
	The carrying amounts of cash and cash equivalents and short-term debt approximate fair value. 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 on Form 10-Q:
		Hierarchy Level of Fair Value Estimates	Carrying		Estimated		Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value		Amount		Fair Value
			Mar. 31, 2014				Mar. 31, 2013				Dec. 31, 2013
			(in millions)
	Financial assets
	Cash and cash equivalents	1	$	1.4	$	1.4	$	2.8	$	2.8	$	8.8	$	8.8
	Notes receivable from Questar	1	30.6		30.6		—		—		—		—
	Financial liabilities
	Notes payable to Questar	1	—		—		132.3		132.3		17.7		17.7
	Long-term debt, including current portion	2	534.5		588.9		386.5		460		534.5		568
	The carrying amounts of cash and cash equivalents approximate fair value. The carrying amounts of notes receivable from and 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 on Form 10-Q:
		Hierarchy Level of Fair Value Estimates	Carrying		Estimated		Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value		Amount		Fair Value
			Mar. 31, 2014				Mar. 31, 2013				Dec. 31, 2013
			(in millions)
	Financial assets
	Cash and cash equivalents	1	$	4.9	$	4.9	$	5.4	$	5.4	$	2.7	$	2.7
	Notes receivable from Questar	1	46.6		46.6		33.1		33.1		29.4		29.4
	Financial liabilities
	Long-term debt	2	458.8		509.4		458.9		537.3		458.9		486
	The carrying amounts of cash and cash equivalents approximate fair value. 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)	3 Months Ended
	Mar. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivatives and Hedging	'
	Note 7 - 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 12 months ended March 31, 2014 and March 31, 2013.
	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. As of March 31, 2014, the Company was not hedging any exposure to variability in future cash flows of forecasted transactions. There were no derivative assets or liabilities outstanding at March 31, 2014, March 31, 2013 or December 31, 2013.

ShareBased_Compensation_Notes

Share-Based Compensation (Notes)	3 Months Ended
	Mar. 31, 2014
Share-based Compensation [Abstract]	'
Share-Based Compensation	'
	Note 8 - Share-Based Compensation
	Questar may issue stock options, restricted shares, RSUs and performance shares to certain of its officers, employees and non-employee directors under the LTSIP. Questar recognizes expense over time as the stock options, restricted shares, RSUs and performance shares vest. Total share-based compensation expense amounted to $3.2 million for the first quarter of 2014 compared to $3.1 million in 2013. Deferred share-based compensation, representing the unvested value of restricted share and RSU awards, amounted to $10.9 million at March 31, 2014. For the first quarter, cash flow from income tax benefits in excess of recognized compensation expense amounted to $0.5 million in 2014 compared to $1.4 million in 2013. There were 4,037,945 shares available for future grants at March 31, 2014.
	There were no unvested stock options at March 31, 2014. No stock options were granted, exercised or forfeited in the first quarter of 2014. Stock option balances under the terms of the LTSIP are summarized below:
	Options Outstanding													Options Exercisable
	Range of exercise							Number outstanding at March 31, 2014		Weighted-average remaining term in years		Weighted-average exercise price		Number exercisable at March 31, 2014	Weighted-average exercise price
	prices
	$	7.84		-	$	11.4		404,174		1.6		$	10.52	404,174	$	10.52
	13.1			-	17.35			313,666		2.3		13.54		313,666	13.54
								717,840		1.9		$	11.84	717,840	$	11.84
	Restricted share grants typically vest in equal installments over a three-year period from the grant date. Several grants vest in a single installment after a specified period. The weighted-average remaining vesting period of unvested restricted shares at March 31, 2014, was 9 months. No restricted shares were granted or forfeited in the first quarter of 2014. Transactions involving restricted shares under the terms of the LTSIP are summarized below:
		Restricted			Price Range						Weighted-Average Price
		Shares
		Outstanding
	Balance at December 31, 2013	392,327			$	15.22	-	$	21.53		$	18.28
	Vested	(212,530	)		15.98		-	21.53			18.6
	Balance at March 31, 2014	179,797			$	15.22	-	$	21.53		$	17.91
	Questar may grant RSUs to certain of its officers, employees and non-employee directors under the LTSIP. One share of Questar common stock will be distributed for each RSU at the time of vesting. RSU grants typically vest in equal installments over a three-year period from the grant date. Several grants vest in a single installment after a specified period. The weighted-average remaining vesting period of unvested RSUs at March 31, 2014, was 21 months. Transactions involving RSUs under the terms of the LTSIP are summarized below:
		RSUs			Price Range						Weighted-Average Price
		Outstanding
	Balance at December 31, 2013	316,268			$	22.17	-	$	25.44		$	23.62
	Granted	346,776			23.6		-	23.63			23.6
	Vested	(119,014	)		22.71		-	25.44			23.66
	Forfeited	(2,456	)		23.6			23.6			23.6
	Balance at March 31, 2014	541,574			$	22.17	-	$	24.26		$	23.6
	Questar may grant RSUs with deferred share distributions (deferred RSUs) to certain of its non-employee directors under the LTSIP. Grants of deferred RSUs typically vest in equal installments over a three-year period from the grant date. Several grants vest in a single installment after a specified period. At March 31, 2014, Questar's outstanding deferred RSUs totaled 91,289 with a weighted-average price of $17.25 per share. The weighted-average remaining vesting period of unvested deferred RSUs at March 31, 2014, was 11 months. The deferred RSU total includes 74,208 units with a weighted-average price of $15.79 that were fully vested as of March 31, 2014. One share of Questar common stock will be distributed for each vested deferred RSU (including accrued reinvested dividend equivalents) at the time of the grantees' separation from service.
	Questar may grant performance shares to certain of its officers under the terms of the LTSIP. The awards are designed to motivate and reward these officers for long-term Company performance and provide an incentive for them to remain with the Company. The target number of performance shares for each officer is subject to adjustment upward or downward based on the Company's total shareholder return relative to a specified peer group of companies over a three-year performance period. Each three-year performance period commences at the beginning of the year of grant. Distributions of performance shares, if any, take place in the quarter following the conclusion of the performance period so long as such officer was employed by the Company or its affiliates as of the last day of the performance period.
	For performance shares granted in 2012 and 2013, half of any award will be distributed in shares of Questar common stock and half in cash. Thereafter, any award will be distributed in shares, with no cash component. For share-settled performance share awards, the grant-date fair value of the awards is amortized to expense over the vesting period. The Monte Carlo simulation method is used to estimate the grant-date fair value of the performance share awards. The liability associated with awards to be settled in cash is adjusted to its estimated fair value through earnings on a quarterly basis. Equity- and liability-based performance share compensation expense amounted to $0.7 million in the first quarter of 2014 and $0.8 million in the first quarter of 2013. The weighted-average remaining vesting period of unvested performance shares at March 31, 2014, was 21 months. Performance share transactions under the terms of the LTSIP are summarized below:
		Target Number of Performance Shares Outstanding			Grant-Date						Weighted- Average Grant-Date Fair Value
					Fair Value Range
	Balance at December 31, 2013	387,879			$	18.23	-	$	39.62		$	27.61
	Granted	139,611			31.07			31.07			31.07
	Payout adjustment(1)	(76,657	)		18.23			18.23			18.23
	Distributed(1)	(51,104	)		18.23			18.23			18.23
	Forfeited	(5,660	)		25.42		-	39.62			33.06
	Balance at March 31, 2014	394,069			$	25.42	-	$	39.62		$	31.8
	(1) Actual shares and cash distributed were determined by multiplying the target shares by 0.40 to reflect Questar's final total shareholder return ranking among the specified peer companies for the performance period from January 1, 2011 through December 31, 2013.
	The above March 31, 2014 balance includes 6,475 vested target performance shares with a weighted-average grant-date fair value of $30.08 and expected distribution dates ranging from the first quarter of 2015 through the first quarter of 2017.
	Certain officers, employees and non-employee directors of former subsidiary QEP Resources held 251,098 Questar stock options with a weighted-average exercise price of $11.33 per share and a weighted-average remaining life of 2.2 years at March 31, 2014.

Operations_by_Line_of_Business

Operations by Line of Business (Notes)	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Operations by Line of Business	'
	Note 9 - 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. 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						12 Months Ended
		March 31,						March 31,
		2014			2013			2014			2013
		(in millions)
	Revenues from Unaffiliated Customers
	Questar Gas	$	396.3		$	418.3		$	963.2		$	912
	Wexpro	12.3			10.3			47.1			37.2
	Questar Pipeline	48			48.3			189.2			200.9
	Other	0.3			—			0.5			—
	Total	$	456.9		$	476.9		$	1,200.00		$	1,150.10
	Revenues from Affiliated Companies
	Questar Gas	$	—		$	0.3		$	0.3		$	2
	Wexpro	89.1			72.8			311.1			281.2
	Questar Pipeline	19.3			19.5			76.5			75.4
	Total	$	108.4		$	92.6		$	387.9		$	358.6
	Operating Income (Loss)
	Questar Gas	$	69.8		$	64.3		$	107.4		$	95.4
	Wexpro	48.5			39.8			176.4			160.7
	Questar Pipeline	30.1			30.2			35.4			122.4
	Corporate and other	(0.1		)	(2.9		)	3.5			(2.3		)
	Total	$	148.3		$	131.4		$	322.7		$	376.2
	Net Income (Loss)
	Questar Gas	$	39.6		$	37		$	55.4		$	49.2
	Wexpro	31.8			26.3			116.1			105.9
	Questar Pipeline	15.7			15.8			8.1			63.9
	Corporate and other	(2.0		)	(6.2		)	(6.2		)	(9.3		)
	Total	$	85.1		$	72.9		$	173.4		$	209.7

Employee_Benefits_Notes

Employee Benefits (Notes)	3 Months Ended
	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]	'
Employee Benefits	'
	Note 10 - 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 2014 estimated net cost for the qualified pension plan is $15.4 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, or to the spouse upon death of the management employee, above the benefit limit defined by the Internal Revenue Service for the qualified plan. The nonqualified pension plan is unfunded; claims are paid from the Company's general funds. The 2014 estimated net cost for the nonqualified pension plan is $3.7 million.
	Components of the qualified and nonqualified net periodic pension cost are listed in the table below:
		3 Months Ended						12 Months Ended
		March 31,						March 31,
		2014			2013			2014			2013
		(in millions)
	Service cost	$	3		$	3.5		$	13.4		$	13.2
	Interest cost	8.4			7.8			31.2			31.4
	Expected return on plan assets	(10.6		)	(9.5		)	(39.2		)	(33.6		)
	Prior service and other costs	0.1			0.3			0.9			1.1
	Recognized net actuarial loss	3.9			6.8			26			26.3
	Net pension cost	$	4.8		$	8.9		$	32.3		$	38.4
	The Company currently estimates a $2.8 million net cost for postretirement benefits other than pensions in 2014, before accretion of a regulatory liability. Net periodic postretirement benefit cost components are listed in the table below:
		3 Months Ended						12 Months Ended
		March 31,						March 31,
		2014			2013			2014			2013
		(in millions)
	Service cost	$	0.2		$	0.2		$	0.7		$	0.8
	Interest cost	1			1			3.7			3.9
	Expected return on plan assets	(0.8		)	(0.7		)	(2.7		)	(2.5		)
	Amortization of transition obligation	—			—			—			1.2
	Recognized net actuarial loss	0.3			0.7			2.6			2.6
	Accretion of regulatory liability	0.2			0.2			0.5			0.3
	Net postretirement benefit cost	$	0.9		$	1.4		$	4.8		$	6.3

Questar_Southern_Trails_Pipeli

Questar Southern Trails Pipeline Eastern Segment Impairment (Notes)	3 Months Ended
	Mar. 31, 2014
Strategic Review of Questar Southern Trails Pipeline and Impairment of Eastern Segment [Abstract]	'
Questar Southern Trails Pipeline Eastern Segment Impairment	'
	Note 11 - Questar Southern Trails Pipeline Eastern Segment Impairment
	During the third quarter of 2013, Questar Pipeline updated its five-year forecast for the eastern segment of Southern Trails Pipeline, which resulted in revised projections of higher operating expenses including right-of-way and pipeline safety costs. Current and projected market rates for natural gas transportation between the San Juan Basin and California markets do not cover these increasing operating expenses. Because of changes in expected cash flows in the third quarter of 2013 and the lack of progress in selling or recontracting this pipeline, Questar Pipeline recorded a noncash impairment of its entire investment in the eastern segment of Southern Trails Pipeline of $80.6 million, or $52.4 million after income taxes. Questar Pipeline used a probability-weighted discounted cash flow analysis that included significant inputs such as Questar Pipeline's cost of capital and assumptions regarding future transportation rates and operating costs.

Wexpro_Acquisition_of_Producin

Wexpro Acquisition of Producing Properties and Inclusion in Wexpro II Agreement (Notes)	3 Months Ended
	Mar. 31, 2014
Wexpro Acquisition of Producing Properties [Abstract]	'
Wexpro Acquisition of Producing Properties and Inclusion in Wexpro II Agreement	'
	Note 12 - Wexpro Acquisition of Producing Properties and Inclusion in Wexpro II Agreement
	On September 4, 2013, Wexpro completed the transaction announced in July 2013 to acquire an additional interest in natural gas-producing properties in the Trail Unit of southwestern Wyoming's Vermillion Basin (Trail acquisition). This acquisition was an addition to the company’s existing Trail assets, which are governed by the 1981 Wexpro Agreement. In January 2014, the Public Service Commission of Utah and the Wyoming Public Service Commission (the Commissions) approved the inclusion of these properties in the Wexpro II Agreement, effective February 1, 2014. The Wexpro II Agreement is modeled after the terms of the original Wexpro Agreement. Under the Wexpro II Agreement, Wexpro may acquire gas development properties and Questar Gas may submit an application to the Commissions to treat these properties similar to the original Wexpro properties. If the Commissions approve the applications, the gas will be developed for the benefit of Questar Gas customers. Wexpro will be entitled to a return on the acquisition costs based on Questar Gas's approved cost of capital. Future development investment will earn returns consistent with the original Wexpro Agreement.

Basis_of_Presentation_of_Inter1

Basis of Presentation of Interim Financial Statements (Policies)	3 Months Ended
	Mar. 31, 2014
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 uses the equity method to account for its investment in an unconsolidated affiliate where it does not have control, but has significant influence. White River Hub, LLC is a limited liability company and FERC-regulated transporter of natural gas. Questar Pipeline owns 50% of White River Hub, LLC and is the operator. Generally, the investment in White River Hub, LLC on the Company's balance sheets equals the Company's proportionate share of equity reported by White River Hub, LLC. The investment is assessed for possible impairment when events indicate that the fair value of the investment may be below the Company'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.
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). 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 dividends 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 are participating securities for the computation of basic earnings per share. The application of the two-class method had an insignificant impact on the calculation of both 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 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 (OPRB) costs are accrued, as the Company records interest expense for hedged interest payments and when the long-term investment is sold or otherwise realized.
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 cash flow hedges and the related income taxes. Income or loss is recognized as the company records interest expense for hedged interest payments.
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.

Basis_of_Presentation_of_Inter2

Basis of Presentation of Interim Financial Statements (Tables)	3 Months Ended
	Mar. 31, 2014
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						12 Months Ended
		March 31,						March 31,
		2014			2013			2014			2013
		(in millions)
	Questar Gas
	Gas purchases	$	92.7		$	103.3		$	176		$	146
	Operator service fee	89.1			72.8			310.9			281.1
	Transportation and storage	22.1			22			80.2			81
	Gathering	4.9			4.6			19.1			19
	Royalties	17.3			11.1			50.5			32.9
	Storage withdrawal, net	33			28.8			3.4			3.3
	Purchased-gas account adjustment	(5.6		)	46.7			(30.3		)	19.4
	Other	1.1			1.3			4.8			5
	Total Questar Gas cost of natural gas sold	254.6			290.6			614.6			587.7
	Elimination of Questar Gas cost of natural gas sold - affiliated parties	(108.2		)	(92.1		)	(387.0		)	(355.8		)
	Total Questar Gas cost of natural gas sold - unaffiliated parties	146.4			198.5			227.6			231.9
	Questar Pipeline
	Total Questar Pipeline cost of sales	1.7			1.2			6.6			7.4
	Other cost of sales	0.1			—			0.2			—
	Total cost of sales	$	148.2		$	199.7		$	234.4		$	239.3

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2014
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		12 Months Ended
		March 31,		March 31,
		2014	2013	2014	2013
		(in millions)
	Weighted-average basic common shares outstanding	175.7	175.3	175.6	175.6
	Potential number of shares issuable under the Company's LTSIP	0.4	0.8	0.5	0.9
	Weighted-average diluted common shares outstanding	176.1	176.1	176.1	176.5

Other_Comprehensive_Income_Tab

Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2014
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 OPRB			Interest rate cash flow hedges			Long-term invest.			Total			Pension and OPRB			Interest rate cash flow hedges			Long-term invest.		Total
		3 Months Ended												3 Months Ended
		March 31, 2014												March 31, 2013
		(in millions)
	AOCI at beginning of period	$	(119.0	)	$	(22.9	)	$	0.1		$	(141.8	)	$	(223.2	)	$	(23.2	)	$	0.1	$	(246.3	)
	Reclassified from AOCI(1)	4.3			0.2			—			4.5			7.8			0.2			—		8
	Income taxes
	Reclassified from AOCI(2)	(1.7		)	(0.1		)	—			(1.8		)	(2.9		)	(0.1		)	—		(3.0		)
	Net other comprehensive income	2.6			0.1			—			2.7			4.9			0.1			—		5
	AOCI at March 31,	$	(116.4	)	$	(22.8	)	$	0.1		$	(139.1	)	$	(218.3	)	$	(23.1	)	$	0.1	$	(241.3	)
		Pension and OPRB			Interest rate cash flow hedges			Long-term invest.			Total
		12 Months Ended
		March 31, 2014
		(in millions)
	AOCI at beginning of period	$	(218.3	)	$	(23.1	)	$	0.1		$	(241.3	)
	OCI before reclassifications	135.8			—			(0.1		)	135.7
	Reclassified from AOCI(1)	29.5			0.5			—			30
	Income taxes
	OCI before reclassifications	(51.9		)	—			0.1			(51.8		)
	Reclassified from AOCI(2)	(11.5		)	(0.2		)	—			(11.7		)
	Total income taxes	(63.4		)	(0.2		)	0.1			(63.5		)
	Net other comprehensive income	101.9			0.3			—			102.2
	AOCI at March 31,	$	(116.4	)	$	(22.8	)	$	0.1		$	(139.1	)
	(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_T

Asset Retirement Obligations (Tables)	3 Months Ended
	Mar. 31, 2014
Asset Retirement Obligation [Abstract]	'
Changes in AROs	'
	Changes in Questar's AROs from the Condensed Consolidated Balance Sheets were as follows:
		3 Months Ended
		March 31,
		2014			2013
		(in millions)
	AROs at beginning of year	$	67.7		$	67.2
	Accretion	0.8			0.8
	Liabilities incurred	0.4			0.4
	Revisions in estimated cash flows	0.4			(6.8		)
	Liabilities settled	(0.7		)	(0.4		)
	AROs at March 31,	$	68.6		$	61.2

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2014
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 on Form 10-Q:
		Hierarchy Level of Fair Value Estimates	Carrying		Estimated		Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value		Amount		Fair Value
			Mar. 31, 2014				Mar. 31, 2013				Dec. 31, 2013
			(in millions)
	Financial assets
	Cash and cash equivalents	1	$	5.6	$	5.6	$	7.2	$	7.2	$	16	$	16
	Long-term investment	1	15.3		15.3		16.1		16.1		17.3		17.3
	Financial liabilities
	Short-term debt	1	157		157		202		202		276		276
	Long-term debt, including current portion	2	1,246.60		1,357.50		1,100.50		1,260.10		1,247.10		1,310.80
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 on Form 10-Q:
		Hierarchy Level of Fair Value Estimates	Carrying		Estimated		Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value		Amount		Fair Value
			Mar. 31, 2014				Mar. 31, 2013				Dec. 31, 2013
			(in millions)
	Financial assets
	Cash and cash equivalents	1	$	1.4	$	1.4	$	2.8	$	2.8	$	8.8	$	8.8
	Notes receivable from Questar	1	30.6		30.6		—		—		—		—
	Financial liabilities
	Notes payable to Questar	1	—		—		132.3		132.3		17.7		17.7
	Long-term debt, including current portion	2	534.5		588.9		386.5		460		534.5		568
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 on Form 10-Q:
		Hierarchy Level of Fair Value Estimates	Carrying		Estimated		Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value		Amount		Fair Value
			Mar. 31, 2014				Mar. 31, 2013				Dec. 31, 2013
			(in millions)
	Financial assets
	Cash and cash equivalents	1	$	4.9	$	4.9	$	5.4	$	5.4	$	2.7	$	2.7
	Notes receivable from Questar	1	46.6		46.6		33.1		33.1		29.4		29.4
	Financial liabilities
	Long-term debt	2	458.8		509.4		458.9		537.3		458.9		486

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2014
Share-based Compensation [Abstract]	'
Options held under the LTSIP, by exercise price range	'
	Stock option balances under the terms of the LTSIP are summarized below:
	Options Outstanding													Options Exercisable
	Range of exercise							Number outstanding at March 31, 2014		Weighted-average remaining term in years		Weighted-average exercise price		Number exercisable at March 31, 2014	Weighted-average exercise price
	prices
	$	7.84		-	$	11.4		404,174		1.6		$	10.52	404,174	$	10.52
	13.1			-	17.35			313,666		2.3		13.54		313,666	13.54
								717,840		1.9		$	11.84	717,840	$	11.84
Transactions involving restricted shares and RSUs under the terms of the LTSIP	'
	Transactions involving restricted shares under the terms of the LTSIP are summarized below:
		Restricted			Price Range						Weighted-Average Price
		Shares
		Outstanding
	Balance at December 31, 2013	392,327			$	15.22	-	$	21.53		$	18.28
	Vested	(212,530	)		15.98		-	21.53			18.6
	Balance at March 31, 2014	179,797			$	15.22	-	$	21.53		$	17.91
	Transactions involving RSUs under the terms of the LTSIP are summarized below:
		RSUs			Price Range						Weighted-Average Price
		Outstanding
	Balance at December 31, 2013	316,268			$	22.17	-	$	25.44		$	23.62
	Granted	346,776			23.6		-	23.63			23.6
	Vested	(119,014	)		22.71		-	25.44			23.66
	Forfeited	(2,456	)		23.6			23.6			23.6
	Balance at March 31, 2014	541,574			$	22.17	-	$	24.26		$	23.6
Transactions involving performance shares under the terms of the LTSIP	'
	Performance share transactions under the terms of the LTSIP are summarized below:
		Target Number of Performance Shares Outstanding			Grant-Date						Weighted- Average Grant-Date Fair Value
					Fair Value Range
	Balance at December 31, 2013	387,879			$	18.23	-	$	39.62		$	27.61
	Granted	139,611			31.07			31.07			31.07
	Payout adjustment(1)	(76,657	)		18.23			18.23			18.23
	Distributed(1)	(51,104	)		18.23			18.23			18.23
	Forfeited	(5,660	)		25.42		-	39.62			33.06
	Balance at March 31, 2014	394,069			$	25.42	-	$	39.62		$	31.8
	(1) Actual shares and cash distributed were determined by multiplying the target shares by 0.40 to reflect Questar's final total shareholder return ranking among the specified peer companies for the performance period from January 1, 2011 through December 31, 2013.

Operations_by_Line_of_Business1

Operations by Line of Business (Tables)	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Summary of operations by line of business	'
	Following is a summary of operations by line of business:
		3 Months Ended						12 Months Ended
		March 31,						March 31,
		2014			2013			2014			2013
		(in millions)
	Revenues from Unaffiliated Customers
	Questar Gas	$	396.3		$	418.3		$	963.2		$	912
	Wexpro	12.3			10.3			47.1			37.2
	Questar Pipeline	48			48.3			189.2			200.9
	Other	0.3			—			0.5			—
	Total	$	456.9		$	476.9		$	1,200.00		$	1,150.10
	Revenues from Affiliated Companies
	Questar Gas	$	—		$	0.3		$	0.3		$	2
	Wexpro	89.1			72.8			311.1			281.2
	Questar Pipeline	19.3			19.5			76.5			75.4
	Total	$	108.4		$	92.6		$	387.9		$	358.6
	Operating Income (Loss)
	Questar Gas	$	69.8		$	64.3		$	107.4		$	95.4
	Wexpro	48.5			39.8			176.4			160.7
	Questar Pipeline	30.1			30.2			35.4			122.4
	Corporate and other	(0.1		)	(2.9		)	3.5			(2.3		)
	Total	$	148.3		$	131.4		$	322.7		$	376.2
	Net Income (Loss)
	Questar Gas	$	39.6		$	37		$	55.4		$	49.2
	Wexpro	31.8			26.3			116.1			105.9
	Questar Pipeline	15.7			15.8			8.1			63.9
	Corporate and other	(2.0		)	(6.2		)	(6.2		)	(9.3		)
	Total	$	85.1		$	72.9		$	173.4		$	209.7

Employee_Benefits_Tables

Employee Benefits (Tables)	3 Months Ended
	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]	'
Schedule of Defined Benefit Plans Disclosures	'
	Net periodic postretirement benefit cost components are listed in the table below:
		3 Months Ended						12 Months Ended
		March 31,						March 31,
		2014			2013			2014			2013
		(in millions)
	Service cost	$	0.2		$	0.2		$	0.7		$	0.8
	Interest cost	1			1			3.7			3.9
	Expected return on plan assets	(0.8		)	(0.7		)	(2.7		)	(2.5		)
	Amortization of transition obligation	—			—			—			1.2
	Recognized net actuarial loss	0.3			0.7			2.6			2.6
	Accretion of regulatory liability	0.2			0.2			0.5			0.3
	Net postretirement benefit cost	$	0.9		$	1.4		$	4.8		$	6.3
	Components of the qualified and nonqualified net periodic pension cost are listed in the table below:
		3 Months Ended						12 Months Ended
		March 31,						March 31,
		2014			2013			2014			2013
		(in millions)
	Service cost	$	3		$	3.5		$	13.4		$	13.2
	Interest cost	8.4			7.8			31.2			31.4
	Expected return on plan assets	(10.6		)	(9.5		)	(39.2		)	(33.6		)
	Prior service and other costs	0.1			0.3			0.9			1.1
	Recognized net actuarial loss	3.9			6.8			26			26.3
	Net pension cost	$	4.8		$	8.9		$	32.3		$	38.4

Nature_of_Business_Details

Nature of Business (Details)	3 Months Ended
	Mar. 31, 2014
	lines_of_business
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Number of principal complementary lines of business	3

Basis_of_Presentation_of_Inter3

Basis of Presentation of Interim Financial Statements (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'	'	'	'
Ownership percentage in unconsolidated affiliate (in hundredths)	50.00%	'	50.00%	'
Cost of Sales [Abstract]	'	'	'	'
Other cost of sales	$0.10	$0	$0.20	$0
Total cost of sales	148.2	199.7	234.4	239.3
Questar Gas [Member]	'	'	'	'
Cost of Sales [Abstract]	'	'	'	'
Gas purchases	92.7	103.3	176	146
Operator service fee	89.1	72.8	310.9	281.1
Transportation and storage	22.1	22	80.2	81
Gathering	4.9	4.6	19.1	19
Royalties	17.3	11.1	50.5	32.9
Storage withdrawal, net	33	28.8	3.4	3.3
Purchased-gas account adjustment	-5.6	46.7	-30.3	19.4
Other	1.1	1.3	4.8	5
Cost of Purchased Oil and Gas	254.6	290.6	614.6	587.7
Elimination of Questar Gas cost of natural gas sold - affiliated parties	-108.2	-92.1	-387	-355.8
Total Questar Gas cost of natural gas sold - unaffiliated parties	146.4	198.5	227.6	231.9
Questar Pipeline [Member]	'	'	'	'
Cost of Sales [Abstract]	'	'	'	'
Total Questar Pipeline cost of sales	$1.70	$1.20	$6.60	$7.40

Earnings_Per_Share_Details

Earnings Per Share (Details)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share [Abstract]	'	'	'	'
Weighted-average basic common shares outstanding (in shares)	175.7	175.3	175.6	175.6
Potential number of shares issuable under the Company's LTSIP (in shares)	0.4	0.8	0.5	0.9
Weighted-average diluted common shares outstanding (in shares)	176.1	176.1	176.1	176.5

Other_Comprehensive_Income_Det

Other Comprehensive Income (Details) (USD $)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2014		Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]	'		'		'		'
AOCI at beginning of period	($141.80)		($246.30)		($241.30)		'
OCI before reclassifications	'		'		135.7		'
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	4.5	[1]	8	[1]	30	[1]	'
Income taxes	'		'		'		'
Attributable to OCI before reclassifications	'		'		-51.8		'
Attributable to amounts reclassified from AOCI	-1.8	[2]	-3	[2]	-11.7	[2]	'
Total income taxes	-1.8		-3		-63.5		11.9
Net other comprehensive income (loss)	2.7		5		102.2		-19.3
AOCI at March 31,	-139.1		-241.3		-139.1		-241.3
Reclassification Adjustment out of Accumulated Other Comphrensive Income [Abstract]	'		'		'		'
Income tax benefit	-50.1		-47.9		-103.5		-121.1
Pension and OPRB	'		'		'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]	'		'		'		'
AOCI at beginning of period	-119		-223.2		-218.3		'
OCI before reclassifications	'		'		135.8		'
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	4.3	[1]	7.8	[1]	29.5	[1]	'
Income taxes	'		'		'		'
Attributable to OCI before reclassifications	'		'		-51.9		'
Attributable to amounts reclassified from AOCI	-1.7	[2]	-2.9	[2]	-11.5	[2]	'
Total income taxes	'		'		-63.4		'
Net other comprehensive income (loss)	2.6		4.9		101.9		'
AOCI at March 31,	-116.4		-218.3		-116.4		-218.3
Long-term invest.	'		'		'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]	'		'		'		'
AOCI at beginning of period	0.1		0.1		0.1		'
OCI before reclassifications	'		'		-0.1		'
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0	[1]	0	[1]	0	[1]	'
Income taxes	'		'		'		'
Attributable to OCI before reclassifications	'		'		0.1		'
Attributable to amounts reclassified from AOCI	0	[2]	0	[2]	0	[2]	'
Total income taxes	'		'		0.1		'
Net other comprehensive income (loss)	0		0		0		'
AOCI at March 31,	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	-22.9		'		-23.1		'
Income taxes	'		'		'		'
Total income taxes	-0.1		-0.1		-0.2		-0.2
Net other comprehensive income (loss)	0.1		0.1		0.3		0.3
AOCI at March 31,	-22.8		-23.1		-22.8		-23.1
Reclassification Adjustment out of Accumulated Other Comphrensive Income [Abstract]	'		'		'		'
Income tax benefit	-9.1		-9.1		-7		-36.9
Questar Pipeline [Member] | Interest rate cash flow hedges	'		'		'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]	'		'		'		'
AOCI at beginning of period	-22.9		-23.2		-23.1		'
OCI before reclassifications	'		'		0		'
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0.2	[1]	0.2	[1]	0.5	[1]	'
Income taxes	'		'		'		'
Attributable to OCI before reclassifications	'		'		0		'
Attributable to amounts reclassified from AOCI	-0.1	[2]	-0.1	[2]	-0.2	[2]	'
Total income taxes	'		'		-0.2		'
Net other comprehensive income (loss)	0.1		0.1		0.3		'
AOCI at March 31,	-22.8		-23.1		-22.8		-23.1
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)	-0.2		-0.2		-0.5		'
Income tax benefit	$0.10		$0.10		$0.20		'
[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_D

Asset Retirement Obligations (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]	'	'
AROs at beginning of year	$67.70	$67.20
Accretion	0.8	0.8
Liabilities incurred	0.4	0.4
Revisions in estimated cash flows	0.4	-6.8
Liabilities settled	-0.7	-0.4
AROs at March 31,	$68.60	$61.20

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
In Millions, unless otherwise specified
Carrying Amount [Member]	'	'	'
Financial assets [Abstract]	'	'	'
Cash and cash equivalents	$5.60	$16	$7.20
Long-term investment	15.3	17.3	16.1
Financial liabilities [Abstract]	'	'	'
Short-term debt	157	276	202
Long-term debt, including current portion	1,246.60	1,247.10	1,100.50
Estimated Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]	'	'	'
Financial assets [Abstract]	'	'	'
Cash and cash equivalents	5.6	16	7.2
Financial liabilities [Abstract]	'	'	'
Short-term debt	157	276	202
Estimated Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]	'	'	'
Financial liabilities [Abstract]	'	'	'
Long-term debt, including current portion	1,357.50	1,310.80	1,260.10
Estimated Fair Value [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]	'	'	'
Financial assets [Abstract]	'	'	'
Long-term investment	15.3	17.3	16.1
Questar Gas [Member] | Carrying Amount [Member]	'	'	'
Financial assets [Abstract]	'	'	'
Cash and cash equivalents	1.4	8.8	2.8
Notes receivable from Questar	30.6	0	0
Financial liabilities [Abstract]	'	'	'
Notes payable to Questar	0	17.7	132.3
Long-term debt, including current portion	534.5	534.5	386.5
Questar Gas [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]	'	'	'
Financial assets [Abstract]	'	'	'
Cash and cash equivalents	1.4	8.8	2.8
Notes receivable from Questar	30.6	0	0
Financial liabilities [Abstract]	'	'	'
Notes payable to Questar	0	17.7	132.3
Questar Gas [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]	'	'	'
Financial liabilities [Abstract]	'	'	'
Long-term debt, including current portion	588.9	568	460
Questar Pipeline [Member] | Carrying Amount [Member]	'	'	'
Financial assets [Abstract]	'	'	'
Cash and cash equivalents	4.9	2.7	5.4
Notes receivable from Questar	46.6	29.4	33.1
Financial liabilities [Abstract]	'	'	'
Long-term debt, including current portion	458.8	458.9	458.9
Questar Pipeline [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]	'	'	'
Financial assets [Abstract]	'	'	'
Cash and cash equivalents	4.9	2.7	5.4
Notes receivable from Questar	46.6	29.4	33.1
Questar Pipeline [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]	'	'	'
Financial liabilities [Abstract]	'	'	'
Long-term debt, including current portion	$509.40	$486	$537.30

Derivatives_and_Hedging_Detail

Derivatives and Hedging (Details) (Cash Flow Hedging [Member], Questar Pipeline [Member], Forward Starting Interest Rate Swaps Terminating Q4 2011 [Member], USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2011
Cash Flow Hedging [Member] | Questar Pipeline [Member] | Forward Starting Interest Rate Swaps Terminating Q4 2011 [Member]	'	'
Derivative [Line Items]	'	'
Notional amount	'	$150,000,000
Debt Instrument, Face Amount	'	180,000,000
Interest payment for terminated derivative instrument	'	37,300,000
Life of long-term debt associated with cash flow hedges	'	'30 years
Pre-tax net losses expected to be reclassified from AOCI to Consolidated statement of income	$500,000	'
Reclassification from accumulated OCI to income, estimated time to transfer	'12 months	'

ShareBased_Compensation_Genera

Share-Based Compensation General (Details) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation [Abstract]	'	'
Share-based compensation	$3.20	$3.10
Deferred share-based compensation on restricted share awards and restricted stock unit awards	10.9	'
Cash flow from income tax benefits in excess of recognized compensation expense	$0.50	$1.40
Shares available for future grant (in shares)	4,037,945	'

ShareBased_Compensation_Stock_

Share-Based Compensation Stock options (Details) (Stock Options [Member], USD $)	3 Months Ended
	Mar. 31, 2014
Stock option transactions under the terms of the LTSIP - shares [Roll Forward]	'
Granted	0
Exercised	0
Forfeited	0
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]	'
Balance at March 31, 2014	$11.84
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]	'
Options Outstanding, Number outstanding at end of period	717,840
Options Outstanding, Weighted-average remaining term (in years and months)	'1 year 11 months
Options Exercisable, Number exercisable at end of period	717,840
Options Exercisable, Weighted-average exercise price	$11.84
Stock options, additional disclosures [Abstract]	'
Number of unvested options at end of period (in shares)	0
Number of Questar stock options held by certain officers, employees and nonemployee directors of QEP (in shares)	251,098
Weighted-average exercise price of Questar stock options awarded to certain officers, employees and nonemployee directors of QEP (in dollars per share)	$11.33
Weighted-average remaining life of Questar stock options held by certain officers, employees and nonemployee directors of QEP (in years)	'2 years 2 months
$7.84 - $11.40 [Member]	'
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]	'
Balance at March 31, 2014	$10.52
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]	'
Range of exercise prices, lower limit	$7.84
Range of exercise prices, upper limit	$11.40
Options Outstanding, Number outstanding at end of period	404,174
Options Outstanding, Weighted-average remaining term (in years and months)	'1 year 7 months
Options Exercisable, Number exercisable at end of period	404,174
Options Exercisable, Weighted-average exercise price	$10.52
$13.10 - $17.35 [Member]	'
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]	'
Balance at March 31, 2014	$13.54
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]	'
Range of exercise prices, lower limit	$13.10
Range of exercise prices, upper limit	$17.35
Options Outstanding, Number outstanding at end of period	313,666
Options Outstanding, Weighted-average remaining term (in years and months)	'2 years 3 months
Options Exercisable, Number exercisable at end of period	313,666
Options Exercisable, Weighted-average exercise price	$13.54

ShareBased_Compensation_Restri

Share-Based Compensation Restricted shares (Details) (Restricted Shares [Member], USD $)	3 Months Ended
	Mar. 31, 2014
Transactions under the terms of the LTSIP - shares [Roll Forward]	'
Balance at December 31, 2013	392,327
Granted	0
Vested	-212,530
Forfeited	0
Balance at March 31, 2014	179,797
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'
Balance at December 31, 2013	$18.28
Vested	$18.60
Balance at March 31, 2014	$17.91
Share-based awards other than options, additional disclosures [Abstract]	'
Vesting period for share-based award (in years)	'3 years
Weighted-average remaining vesting period of share-based awards (in months)	'9 months
Minimum [Member]	'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'
Balance at December 31, 2013	$15.22
Vested	$15.98
Balance at March 31, 2014	$15.22
Maximum [Member]	'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'
Balance at December 31, 2013	$21.53
Vested	$21.53
Balance at March 31, 2014	$21.53

ShareBased_Compensation_Restri1

Share-Based Compensation Restricted stock units (Details) (USD $)	3 Months Ended
	Mar. 31, 2014
Restricted Stock Units (RSUs) [Member]	'
Transactions under the terms of the LTSIP - shares [Roll Forward]	'
Balance at December 31, 2013	316,268
Granted	346,776
Vested	-119,014
Forfeited	-2,456
Balance at March 31, 2014	541,574
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'
Balance at December 31, 2013	$23.62
Granted	$23.60
Vested	$23.66
Forfeited	$23.60
Balance at March 31, 2014	$23.60
Share-based awards other than options, additional disclosures [Abstract]	'
Vesting period for share-based award (in years)	'3 years
Weighted-average remaining vesting period of share-based awards (in months)	'21 months
Weighted-average price of deferred restricted stock units outstanding (in shares)	$23.60
Number of shares of common stock to be issued for each vested restricted stock unit (RSU)	1
Restricted Stock Units (RSUs) [Member] | Minimum [Member]	'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'
Balance at December 31, 2013	$22.17
Granted	$23.60
Vested	$22.71
Forfeited	$23.60
Balance at March 31, 2014	$22.17
Share-based awards other than options, additional disclosures [Abstract]	'
Weighted-average price of deferred restricted stock units outstanding (in shares)	$22.17
Restricted Stock Units (RSUs) [Member] | Maximum [Member]	'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'
Balance at December 31, 2013	$25.44
Granted	$23.63
Vested	$25.44
Forfeited	$23.60
Balance at March 31, 2014	$24.26
Share-based awards other than options, additional disclosures [Abstract]	'
Weighted-average price of deferred restricted stock units outstanding (in shares)	$24.26
Deferred Restricted Stock Units (RSUs) [Member]	'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'
Balance at March 31, 2014	$17.25
Share-based awards other than options, additional disclosures [Abstract]	'
Vesting period for share-based award (in years)	'3 years
Weighted-average remaining vesting period of share-based awards (in months)	'11 months
Number of deferred restricted stock units outstanding (in shares)	91,289
Weighted-average price of deferred restricted stock units outstanding (in shares)	$17.25
Number of shares of common stock to be issued for each vested restricted stock unit (RSU)	1
Deferred Restricted Stock Units (RSUs) [Member] | Vested Undistributed [Member]	'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'
Balance at March 31, 2014	$15.79
Share-based awards other than options, additional disclosures [Abstract]	'
Number of deferred restricted stock units outstanding (in shares)	74,208
Weighted-average price of deferred restricted stock units outstanding (in shares)	$15.79

ShareBased_Compensation_Perfor

Share-Based Compensation Performance shares (Details) (Performance Shares [Member], USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Transactions under the terms of the LTSIP - shares [Roll Forward]	'		'
Balance at December 31, 2013	387,879		'
Granted	139,611		'
Payout adjustment	-76,657	[1]	'
Distributed	-51,104	[1]	'
Forfeited	-5,660		'
Balance at March 31, 2014	394,069		'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'		'
Balance at December 31, 2013	$27.61		'
Granted	$31.07		'
Payout adjustment	$18.23	[1]	'
Distributed	$18.23	[1]	'
Forfeited	$33.06		'
Balance at March 31, 2014	$31.80		'
Share-based awards other than options, additional disclosures [Abstract]	'		'
Performance period that the target number of performance shares for each exectutive officer is subject to adjustment based on the company's performance (in years)	'3 years		'
Equity- and liability-based performance share compensation expense	$0.70		$0.80
Weighted-average remaining vesting period of share-based awards (in months)	'21 months		'
Performance share payout adjustment factor (in hundredths)	0.4		'
Weighted-average grant-date fair value of vested undistributed performance shares outstanding (in shares)	$31.80		'
Vested Undistributed [Member]	'		'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'		'
Balance at March 31, 2014	$30.08		'
Share-based awards other than options, additional disclosures [Abstract]	'		'
Number of vested undistributed performance shares outstanding (in shares)	6,475		'
Weighted-average grant-date fair value of vested undistributed performance shares outstanding (in shares)	$30.08		'
Minimum [Member]	'		'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'		'
Balance at December 31, 2013	$18.23		'
Granted	$31.07		'
Payout adjustment	$18.23	[1]	'
Distributed	$18.23	[1]	'
Forfeited	$25.42		'
Balance at March 31, 2014	$25.42		'
Share-based awards other than options, additional disclosures [Abstract]	'		'
Weighted-average grant-date fair value of vested undistributed performance shares outstanding (in shares)	$25.42		'
Minimum [Member] | Vested Undistributed [Member]	'		'
Share-based awards other than options, additional disclosures [Abstract]	'		'
The date the actual performance shares (if any) will be distributed	'first quarter of 2015		'
Maximum [Member]	'		'
Transactions under the terms of LTSIP - grant-date fair value [Roll Forward]	'		'
Balance at December 31, 2013	$39.62		'
Granted	$31.07		'
Payout adjustment	$18.23	[1]	'
Distributed	$18.23	[1]	'
Forfeited	$39.62		'
Balance at March 31, 2014	$39.62		'
Share-based awards other than options, additional disclosures [Abstract]	'		'
Weighted-average grant-date fair value of vested undistributed performance shares outstanding (in shares)	$39.62		'
Maximum [Member] | Vested Undistributed [Member]	'		'
Share-based awards other than options, additional disclosures [Abstract]	'		'
The date the actual performance shares (if any) will be distributed	'first quarter of 2017		'
[1]	Actual shares and cash distributed were determined by multiplying the target shares by 0.40 to reflect Questar's final total shareholder return ranking among the specified peer companies for the performance period from January 1, 2011 through December 31, 2013.

Operations_by_Line_of_Business2

Operations by Line of Business (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
	lines_of_business
Segment Reporting Information [Line Items]	'	'	'	'
Number of principal complementary lines of business	3	'	'	'
Revenues from Unaffiliated Customers	$456.90	$476.90	$1,200	$1,150.10
Operating Income (Loss)	148.3	131.4	322.7	376.2
Net Income (Loss)	85.1	72.9	173.4	209.7
Questar Gas [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues from Unaffiliated Customers	396.3	418.3	963.2	912
Operating Income (Loss)	69.8	64.3	107.4	95.4
Net Income (Loss)	39.6	37	55.4	49.2
Wexpro [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues from Unaffiliated Customers	12.3	10.3	47.1	37.2
Operating Income (Loss)	48.5	39.8	176.4	160.7
Net Income (Loss)	31.8	26.3	116.1	105.9
Questar Pipeline [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues from Unaffiliated Customers	48	48.3	189.2	200.9
Operating Income (Loss)	30.1	30.2	35.4	122.4
Net Income (Loss)	15.7	15.8	8.1	63.9
Questar Corp and Other [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues from Unaffiliated Customers	0.3	0	0.5	0
Operating Income (Loss)	-0.1	-2.9	3.5	-2.3
Net Income (Loss)	-2	-6.2	-6.2	-9.3
Intersegment Eliminations [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues from Unaffiliated Customers	108.4	92.6	387.9	358.6
Intersegment Eliminations [Member] | Questar Gas [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues from Unaffiliated Customers	0	0.3	0.3	2
Intersegment Eliminations [Member] | Wexpro [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues from Unaffiliated Customers	89.1	72.8	311.1	281.2
Intersegment Eliminations [Member] | Questar Pipeline [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Revenues from Unaffiliated Customers	$19.30	$19.50	$76.50	$75.40

Employee_Benefits_Details

Employee Benefits (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Qualified and nonqualified pension plans [Member]	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Service cost	$3	$3.50	$13.40	$13.20
Interest cost	8.4	7.8	31.2	31.4
Expected return on plan assets	-10.6	-9.5	-39.2	-33.6
Prior service and other costs	0.1	0.3	0.9	1.1
Recognized net actuarial loss	3.9	6.8	26	26.3
Net benefit cost	4.8	8.9	32.3	38.4
Estimated qualified pension plan cost for current fiscal year	15.4	'	15.4	'
Estimated nonqualified pension plan cost for current fiscal year	3.7	'	3.7	'
Postretirement benefits plan [Member]	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Service cost	0.2	0.2	0.7	0.8
Interest cost	1	1	3.7	3.9
Expected return on plan assets	-0.8	-0.7	-2.7	-2.5
Amortization of transition obligation	0	0	0	1.2
Recognized net actuarial loss	0.3	0.7	2.6	2.6
Accretion of regulatory liability	0.2	0.2	0.5	0.3
Net benefit cost	0.9	1.4	4.8	6.3
Estimated postretirement benefits cost for current fiscal year, before accretion of regulatory liability	$2.80	'	$2.80	'

Questar_Southern_Trails_Pipeli1

Questar Southern Trails Pipeline Eastern Segment Impairment (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Property, Plant and Equipment [Line Items]	'	'	'	'
Pre-tax asset impairment charge	$0	$0	$80.60	$0
Questar Pipeline [Member]	'	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'	'
Pre-tax asset impairment charge	0	0	80.6	0
Questar Pipeline [Member] | Questar Southern Trails Pipeline - Eastern Segment [Member]	'	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'	'
Pre-tax asset impairment charge	'	'	80.6	'
After-tax asset impairment charge	'	'	$52.40	'

Wexpro_Acquisition_of_Producin1

Wexpro Acquisition of Producing Properties and Inclusion in Wexpro II Agreement (Details)	3 Months Ended
	Mar. 31, 2014
Business Acquisition [Line Items]	'
Business Acquisition, Effective Date of Acquisition	4-Sep-13
Business Acquisition, Date of Acquisition Agreement	25-Jul-13
Business Acquisition, Description of Acquired Entity	'an additional interest in natural gas-producing properties in the Trail Unit of southwestern Wyoming's Vermillion Basin
Date of Acquisition's Inclusion under Wexpro II Agreement	1-Feb-14