Rate Regulation (Tables)

12 Months Ended

Dec. 31, 2013

Regulated Operations [Abstract]

Details of regulatory assets and liabilities

The following table details regulatory assets and liabilities:

	December 31, 2013				December 31, 2012
	Current		Noncurrent		Current		Noncurrent
	(in millions)
Regulatory assets:
Questar Gas
Purchased-gas adjustment	$	—	$	—	$	15.2	$	—
DSM	11.2		—		11.0		—
Deferred production taxes	5.7		—		5.0		—
Deferred royalties	5.2		—		6.3		—
Contract withholding	8.1		—		3.5		—
Cost of reacquired debt	—		4.8		—		5.3
Pipeline integrity costs	—		9.3		—		8.7
ARO cost-of-service gas wells	—		2.0		—		2.4
Total Questar Gas regulatory assets	30.2		16.1		41.0		16.4
Questar Pipeline
Gas imbalance	5.3		—		4.4		—
Revenue sharing	0.3		—		1.3		—
Cost of reacquired debt	—		2.6		—		3.0
Income taxes recoverable from customers	—		0.6		—		0.9
Other	—		1.2		—		1.3
Total Questar Pipeline regulatory assets	5.6		4.4		5.7		5.2
Total regulatory assets	$	35.8	$	20.5	$	46.7	$	21.6
Regulatory liabilities:
Questar Gas
Purchased-gas adjustment	$	7.4	$	—	$	—	$	—
CET	3.3		—		4.2		—
Cost of plant removal	—		52.7		—		46.2
Income taxes refundable to customers	—		0.3		—		0.5
Other	0.4		—		0.1		—
Total Questar Gas regulatory liabilities	11.1		53.0		4.3		46.7
Questar Pipeline
Gas imbalance	3.0		—		1.4		—
Revenue sharing	—		—		0.1		—
Postretirement medical	—		8.2		—		7.7
Total Questar Pipeline regulatory liabilities	3.0		8.2		1.5		7.7
Total regulatory liabilities	$	14.1	$	61.2	$	5.8	$	54.4