Supplemental Gas and Oil Information (Unaudited) Results of Operations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Results of Operations [Abstract]
Revenues (1)	$ 1,901.2	[1]	$ 1,393.4	[1]	$ 1,703.4	[1]
Production costs	583.3		501.1		433.3
Exploration expenses	11.9		11.2		10.5
Depreciation, depletion and amortization	954.2		838.4		707.4
Abandonment and impairment	93.0		133.0		218.2
Total expenses	1,642.4		1,483.7		1,369.4
Income before income taxes	258.8		(90.3)		334.0
Income taxes	(96.3)		33.6		(119.0)
Results of operations from producing activities excluding allocated corporate overhead and interest expenses	$ 162.5		$ (56.7)		$ 215.0

[1] Revenue for the year ended December 31, 2011, reflect the impact of QEP's settled derivative contracts which during the years ended December 31, 2013 and 2012, are reflected below operating income (loss) on the Consolidated Statements of Operations. See Note 7 - Derivative Contracts.