Derivative Financial Instruments (Details 1) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commodity Derivatives [Abstract]
Realized (loss) gain on commodity derivatives - natural gas									$ (20,552,000)	$ 303,966,000	$ 213,349,000
Realized (loss) gain on commodity derivatives - crude oil									(326,000)	0	0
Unrealized loss (gain) on commodity derivatives									(25,876,000)	(230,385,000)	100,383,000
Gain loss on commodity derivatives	$ (26,204,000)	$ 2,074,000	$ 22,091,000	$ (44,715,000)	$ (3,519,000)	$ (9,896,000)	$ (33,287,000)	$ 120,283,000	$ (46,754,000)	$ 73,581,000	$ 313,732,000