Derivative Instruments (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of realized and unrealized gains (losses) on derivative instruments
Derivative, Gain (Loss) on Derivative, Net, Total	$ 868,201	$ 491,689	$ 225,904
Revenue
Summary of realized and unrealized gains (losses) on derivative instruments
Commodity derivative fair value gains	868,201	491,689	179,546
Discontinued operations
Summary of realized and unrealized gains (losses) on derivative instruments
Commodity derivative fair value gains			$ 46,358