Rate Regulation (Tables)

12 Months Ended

Dec. 31, 2011

Notes to Financial Statements [Abstract]

Details of regulatory assets and liabilities

The following table details regulatory assets and liabilities:

	December 31, 2011				December 31, 2010
	Current		Noncurrent		Current		Noncurrent
	(in millions)
Regulatory assets:
Questar Pipeline
Gas imbalance	$	2.8	$	—	$	0.8	$	—
Revenue sharing	2.4		—		—		—
Cost of reacquired debt	—		3.3		—		3.7
Income taxes recoverable from customers	—		1.2		—		1.6
Other	—		1.4		—		1.4
Total Questar Pipeline regulatory assets	5.2		5.9		0.8		6.7
Questar Gas
DSM	24.2		—		39.7		—
Purchased-gas adjustment	—		—		10.7		—
Deferred production taxes	2.3		—		2.3		—
Cost of reacquired debt	—		5.9		—		6.4
Pipeline integrity costs	—		6.5		—		5.6
ARO cost-of-service gas wells	—		2.7		—		3.0
Total Questar Gas regulatory assets	26.5		15.1		52.7		15.0
Total regulatory assets	$	31.7	$	21.0	$	53.5	$	21.7
Regulatory liabilities:
Questar Pipeline
Gas imbalance	$	0.9	$	—	$	3.1	$	—
Revenue sharing	0.3		—		0.1		—
Postretirement medical	—		7.4		—		6.9
Total Questar Pipeline regulatory liabilities	1.2		7.4		3.2		6.9
Questar Gas
Purchased-gas adjustment	10.8		—		—		—
CET	3.2		—		2.8		—
Other	0.2		—		—		—
Income taxes refundable to customers	—		0.7		—		0.9
Total Questar Gas regulatory liabilities	14.2		0.7		2.8		0.9
Total regulatory liabilities	$	15.4	$	8.1	$	6.0	$	7.8