Disclosure About Oil and Gas Producing Activities (Unaudited) (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flow Relating to Proved Oil and Gas Reserves [Roll Forward]
Standardized Measure, beginning	$ 1,894,317,000	$ 3,796,056,000	$ 3,525,568,000
Net revisions of previous quantity estimates	(1,089,316,000)	(2,516,159,000)	(964,987,000)
Extensions, discoveries and other changes	2,098,644,000	858,951,000	2,173,103,000
Changes in future development costs	(252,992,000)	952,067,000	(741,658,000)
Sales of oil and gas, net of production costs	(720,826,000)	(625,745,000)	(896,434,000)
Net change in prices and production costs	1,204,041,000	(2,912,698,000)	108,108,000
Development costs incurred during the period that reduce future development costs	171,149,000	316,394,000	464,880,000
Accretion of discount	226,326,000	529,696,000	499,358,000
Net changes in production rates and other	145,289,000	363,788,000	(338,982,000)
Net change in income taxes	(574,859,000)	1,131,967,000	(32,900,000)
Aggregrate changes	1,293,652,000	(1,901,739,000)	270,488,000
Standardized Measure, ending	3,187,969,000	1,894,317,000	3,796,056,000
Acquistion of reserves	$ 86,196,000	$ 0	$ 0