Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended				12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2013 bbl lines_of_business	Dec. 31, 2012	Dec. 31, 2011
Nature of Business [Abstract]
Number Of Business Lines					3
Revenue Recognition [Abstract]
After tax rate of return allowed per Wexpro agreement (In hundredths)	20.00%				20.00%
Percentage of operating income retained by Wexpro after expenses (in hundredths)	46.00%				46.00%
Cost of Sales [Abstract]
Other cost of sales					$ 100,000	$ 0	$ 0
Total cost of sales					285,900,000	192,300,000	321,500,000
Cash and Cash Equivalents [Abstract]
Cash equivalent maturity maximum (months)					3 months
Depreciation, depletion and amortization [Abstract]
Barrel of oil conversion to 6,000 cubic feet of natural gas					1
Impairment of Long-Lived Assets [Abstract]
Asset impairment	0	80,600,000	0	0	80,600,000	0	0
Capitalized Interest and Allowance for Funds Used During Construction [Abstract]
AFUDC (recorded as an increase in interest and other income)					6,300,000	2,300,000	4,400,000
Capitalized interest costs (recorded as a reduction of interest expense)					800,000	200,000	600,000
Credit Risk [Abstract]
Bad debt expense					200,000	1,200,000	2,400,000
Allowance for bad debts	1,700,000				1,700,000	3,100,000
Income Taxes [Abstract]
Unrecognized tax benefits	0				0	0	0
Percent of capital expenditures deductible for federal income tax purposes under current statutes (in hundredths)					50.00%		100.00%
Estimated net operating loss (NOL) carryforward	30,000,000				30,000,000
Estimated taxable income					153,800,000
Questar Gas [Member]
Revenue Recognition [Abstract]
Rate Adjustment Time Period	6 months				6 months
Deferred CET adjustments amortization period	12 months				12 months
Rate adjustment limitation as a percent of non-gas revenues (In hundredths)	5.00%				5.00%
Cost of Sales [Abstract]
Gas purchases					186,600,000	104,200,000	221,200,000
Operator service fee					294,600,000	274,000,000	253,400,000
Transportation and storage					80,100,000	79,600,000	78,400,000
Gathering					18,800,000	20,500,000	25,000,000
Royalties					44,300,000	32,000,000	38,900,000
Storage (injection) withdrawal, net					(800,000)	1,900,000	3,000,000
Purchased-gas account adjustment					22,000,000	16,100,000	20,600,000
Other					5,000,000	5,000,000	5,200,000
Total Questar Gas cost of natural gas sold					650,600,000	533,300,000	645,700,000
Elimination of Questar Gas cost of natural gas sold - affiliated parties					(370,900,000)	(347,700,000)	(327,300,000)
Total Questar Gas cost of natural gas sold - unaffiliated parties					279,700,000	185,600,000	318,400,000
Contributions in aid of construction [Abstract]
Time period contributions are refundable if other customers pay to connect to the line (in years)					5 years
Time period if no other customers connect to the line the funds are not refundable (in years)					5 years
Depreciation, depletion and amortization [Abstract]
Questar Gas distribution plant					2.70%	2.80%	2.80%
Capitalized Interest and Allowance for Funds Used During Construction [Abstract]
Capitalized interest costs (recorded as a reduction of interest expense)					200,000	100,000	100,000
Credit Risk [Abstract]
Time period in months uncollected accounts are written off					6 months
Wexpro [Member]
Depreciation, depletion and amortization [Abstract]
Cost-of-service gas and oil properties, per Mcfe					1.56	1.49	1.49
Capitalized Interest and Allowance for Funds Used During Construction [Abstract]
AFUDC (recorded as an increase in interest and other income)					4,600,000	2,100,000	3,300,000
Questar Pipeline [Member]
Investment in Unconsolidated Affiliate [Abstract]
Ownership percentage in unconsolidated affiliate (in hundredths)	50.00%				50.00%
Cost of Sales [Abstract]
Total Questar Pipeline cost of sales					6,100,000	6,700,000	3,100,000
Depreciation, depletion and amortization [Abstract]
Questar Pipeline transportation, storage and other energy services					3.40%	3.40%	3.50%
Impairment of Long-Lived Assets [Abstract]
Asset impairment					80,600,000	0	0
Capitalized Interest and Allowance for Funds Used During Construction [Abstract]
AFUDC (recorded as an increase in interest and other income)					1,700,000	200,000	1,100,000
Capitalized interest costs (recorded as a reduction of interest expense)					$ 600,000	$ 100,000	$ 500,000