Impairment Fair Value and Ceiling Test (Details 2) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2015	Mar. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Provision for Loss (Gain) on Disposal, before Income Tax	$ 400.0
Discontinued Operation, Provision for Loss (Gain) on Disposal, Net of Tax	$ 252.0
Impairment of Oil and Gas Properties		$ 500.4
Impairment of oil and gas properties, after tax		$ 315.3