CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income	$ 161.2	$ 212.0	$ 207.9
Pension and other postretirement benefits
Change in unrecognized actuarial loss	167.7	(35.7)	(162.9)
Change in unrecognized prior service cost	1.1	2.7	3.0
Interest rate cash flow hedges	0.5	0.4	(37.2)
Change in fair value of long-term investment	(0.1)	0.1	0
Income taxes	(64.7)	12.3	75.0
Net other comprehensive income (loss)	104.5	(20.2)	(122.1)
COMPREHENSIVE INCOME	265.7	191.8	85.8
Questar Pipeline [Member]
Net income	8.2	64.7	67.9
Pension and other postretirement benefits
Interest rate cash flow hedges	0.5	0.4	(37.2)
Income taxes	(0.2)	(0.2)	13.8
Net other comprehensive income (loss)	0.3	0.2	(23.4)
COMPREHENSIVE INCOME	$ 8.5	$ 64.9	$ 44.5