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, 2014 bbl lines_of_business	Dec. 31, 2013	Dec. 31, 2012
Nature of Business [Abstract]
Number Of Business Lines					3
Revenue Recognition [Abstract]
Percentage of operating income retained by Wexpro after expenses (in hundredths)					46.00%
Cost of Sales [Abstract]
Other cost of sales					$ 900,000	$ 100,000	$ 0
Total cost of sales					186,300,000	285,900,000	192,300,000
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]
Abandonment and impairment	0	80,600,000	0	0	2,000,000	80,600,000	0
Capitalized Interest and Allowance for Funds Used During Construction [Abstract]
AFUDC (recorded as an increase in interest and other income)					2,800,000	6,300,000	2,300,000
Capitalized interest costs (recorded as a reduction of interest expense)					1,000,000	800,000	200,000
Credit Risk [Abstract]
Bad debt expense					1,700,000	200,000	1,200,000
Allowance for bad debts	1,700,000				1,700,000	1,700,000
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%	50.00%	50.00%
Estimated net operating loss (NOL) carryforward							26,900,000
Questar Gas [Member]
Revenue Recognition [Abstract]
Rate Adjustment Time Period					6 months
Deferred CET adjustments amortization period					12 months
Rate adjustment limitation as a percent of non-gas revenues (In hundredths)					5.00%
Cost of Sales [Abstract]
Gas purchases					136,500,000	186,600,000	104,200,000
Operator service fee					349,700,000	294,600,000	274,000,000
Transportation and storage					79,600,000	80,100,000	79,600,000
Gathering					21,000,000	18,800,000	20,500,000
Royalties					60,100,000	44,300,000	32,000,000
Storage (injection) withdrawal, net					(1,100,000)	(800,000)	1,900,000
Purchased-gas account adjustment					(45,800,000)	22,000,000	16,100,000
Other					4,800,000	5,000,000	5,000,000
Total cost of natural gas sold (excluding operating expenses shown separately) / Total Questar Gas cost of natural gas sold					604,800,000	650,600,000	533,300,000
Elimination of Questar Gas cost of natural gas sold - affiliated companies					(423,400,000)	(370,900,000)	(347,700,000)
Total Questar Gas cost of natural gas sold - unaffiliated parties					181,400,000	279,700,000	185,600,000
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%	2.70%	2.80%
Capitalized Interest and Allowance for Funds Used During Construction [Abstract]
AFUDC (recorded as an increase in interest and other income)					900,000	0	0
Capitalized interest costs (recorded as a reduction of interest expense)					500,000	200,000	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					1.75	1.56	1.49
Impairment of Long-Lived Assets [Abstract]
Abandonment and impairment					2,000,000
Capitalized Interest and Allowance for Funds Used During Construction [Abstract]
AFUDC (recorded as an increase in interest and other income)					800,000	4,600,000	2,100,000
Questar Pipeline [Member]
Investment in Unconsolidated Affiliate [Abstract]
Ownership percentage in unconsolidated affiliate (in hundredths)					50.00%
Cost of Sales [Abstract]
Total Questar Pipeline cost of sales					4,000,000	6,100,000	6,700,000
Depreciation, depletion and amortization [Abstract]
Questar Pipeline transportation, storage and other energy services					3.20%	3.40%	3.40%
Impairment of Long-Lived Assets [Abstract]
Abandonment and impairment					0	80,600,000	0
Capitalized Interest and Allowance for Funds Used During Construction [Abstract]
AFUDC (recorded as an increase in interest and other income)					1,100,000	1,700,000	200,000
Capitalized interest costs (recorded as a reduction of interest expense)					$ 500,000	$ 600,000	$ 100,000