Supplemental Gas Data PV-10 (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Revenues	$ 14,804,398	$ 16,723,795	$ 7,975,195
Production costs	(5,262,635)	(5,175,563)	(3,123,532)
Development costs	(1,674,829)	(2,720,243)	(995,569)
Income tax expense	(2,989,435)	(3,354,444)	(1,465,075)
Future Net Cash Flows	4,877,499	5,473,545	2,391,019
Discounted to present value at a 10% annual rate	(3,130,318)	(3,812,724)	(1,496,668)
Total standardized measure of discounted net cash flows	$ 1,747,181	$ 1,660,821	$ 894,351