Rate Regulation (Tables)

12 Months Ended

Dec. 31, 2012

Regulated Operations [Abstract]

Details of regulatory assets and liabilities

The following table details regulatory assets and liabilities:

	December 31, 2012				December 31, 2011
	Current		Noncurrent		Current		Noncurrent
	(in millions)
Regulatory assets:
Questar Gas
Purchased-gas adjustment	$	15.2	$	—	$	—	$	—
DSM	11.0		—		24.2		—
Deferred production taxes	5.0		—		2.3		—
Deferred royalties	6.3		—		—		—
Cost of reacquired debt	—		5.3		—		5.9
Pipeline integrity costs	—		8.7		—		6.5
ARO cost-of-service gas wells	—		2.4		—		2.7
Other	3.5		—		—		—
Total Questar Gas regulatory assets	41.0		16.4		26.5		15.1
Questar Pipeline
Gas imbalance	4.4		—		2.8		—
Revenue sharing	1.3		—		2.4		—
Cost of reacquired debt	—		3.0		—		3.3
Income taxes recoverable from customers	—		0.9		—		1.2
Other	—		1.3		—		1.4
Total Questar Pipeline regulatory assets	5.7		5.2		5.2		5.9
Total regulatory assets	$	46.7	$	21.6	$	31.7	$	21.0
Regulatory liabilities:
Questar Gas
Purchased-gas adjustment	$	—	$	—	$	10.8	$	—
CET	4.2		—		3.2		—
Income taxes refundable to customers	—		0.5		—		0.7
Other	0.1		—		0.2		—
Total Questar Gas regulatory liabilities	4.3		0.5		14.2		0.7
Questar Pipeline
Gas imbalance	1.4		—		0.9		—
Revenue sharing	0.1		—		0.3		—
Postretirement medical	—		7.7		—		7.4
Total Questar Pipeline regulatory liabilities	1.5		7.7		1.2		7.4
Total regulatory liabilities	$	5.8	$	8.2	$	15.4	$	8.1