Rate Regulation (Tables)

12 Months Ended

Dec. 31, 2014

Regulated Operations [Abstract]

Details of regulatory assets and liabilities

The following table details regulatory assets and liabilities:

	December 31, 2014				December 31, 2013
	Current		Noncurrent		Current		Noncurrent
	(in millions)
Regulatory assets:
Questar Gas
Purchased-gas adjustment	$	39.2	$	—	$	—	$	—
Demand-side management	—		—		11.2		—
Contract withholding	13.6		—		8.1		—
Deferred cost-of-service gas charges	25.5		9.3		10.9		2.0
Cost of reacquired debt	—		4.3		—		4.8
Pipeline integrity costs	—		7.7		—		9.3
Total Questar Gas regulatory assets	78.3		21.3		30.2		16.1
Questar Pipeline
Gas imbalance	1.2		—		5.3		—
Revenue sharing	0.1		—		0.3		—
Cost of reacquired debt	—		2.2		—		2.6
Income taxes recoverable from customers	—		0.3		—		0.6
Other	—		1.2		—		1.2
Total Questar Pipeline regulatory assets	1.3		3.7		5.6		4.4
Total regulatory assets	$	79.6	$	25.0	$	35.8	$	20.5
Regulatory liabilities:
Questar Gas
Purchased-gas adjustment	$	—	$	—	$	7.4	$	—
Demand-side management	0.3		—		—		—
CET	12.1		—		3.3		—
Cost of plant removal	—		60.7		—		52.7
Income taxes refundable to customers	—		0.2		—		0.3
Other	0.1		—		0.4		—
Total Questar Gas regulatory liabilities	12.5		60.9		11.1		53.0
Questar Pipeline
Gas imbalance	0.8		—		3.0		—
Revenue sharing	0.1		—		—		—
Postretirement medical	—		9.0		—		8.2
Total Questar Pipeline regulatory liabilities	0.9		9.0		3.0		8.2
Total regulatory liabilities	$	13.4	$	69.9	$	14.1	$	61.2