Asset Retirement Obligations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014		Sep. 30, 2014		Dec. 31, 2013
Liabilities Settled Through Divestiture	$ 20.2
Asset retirement obligations	162.3		162.3		163.3
Asset Retirement Obligation, Current	0.9		0.9		1.8
ARO Liability [Roll Forward]
ARO liability, Beginning Balance			165.1	[1]
Accretion			4.9
Liabilities incurred			15.5	[2]
Revisions			(0.3)
Liabilities settled			(22.0)	[3]
ARO liability, Ending Balance	163.2	[4]	163.2	[4]
Midstream Business Held For Sale [Member]
Asset retirement obligations	29.9		29.9		28.5
Permian Basin [Member]
ARO Liability [Roll Forward]
Liabilities incurred			$ 9.7

[1] Excludes $28.5 million of ARO classified as liabilities held for sale on the Condensed Consolidated Balance Sheet.

[2] Additions include $9.7 million related to the Permian Basin Acquisition (see Note 3 - Acquisitions and Divestitures).

[3] Settlements include $20.2 million related to the property sales in the second quarter of 2014 (see Note 3 - Acquisitions and Divestitures).

[4] Excludes $29.9 million of ARO classified as liabilities held for sale on the Condensed Consolidated Balance Sheet.