Debt Short-term Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Short-term Debt [Line Items]
Commercial paper with various interest rates	$ 276,000,000	$ 263,000,000
Revolving credit arrangement [Member]
Short-term Debt [Line Items]
Revolving credit facility credit commitments	750,000,000	500,000,000
Revolving credit facility, maturity date	Apr. 19, 2018	Aug. 31, 2016
Additional long-term borrowing permitted under credit facility amendment	150,000,000
Consolidated funded debt percentage of consolidated capital permitted under credit facility amendment	70.00%
Commercial paper with various interest rates	0
Commercial paper [Member]
Short-term Debt [Line Items]
Commercial paper with various interest rates	276,000,000	263,000,000
Weighted-average interest rate at end of year	0.27%	0.31%
Questar Gas [Member]
Short-term Debt [Line Items]
Notes payable to parent	17,700,000	166,100,000
Questar Gas [Member] | Notes payable to Questar [Member]
Short-term Debt [Line Items]
Notes payable to parent	17,700,000	166,100,000
Weighted-average interest rate at end of year	0.30%	0.39%
Questar Pipeline [Member] | Notes payable to Questar [Member]
Short-term Debt [Line Items]
Notes payable to parent	$ 0	$ 0