Supplemental Gas Data PV-10 Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Revenues	$ 21,602,594	$ 11,777,550	$ 14,804,398
Net changes in sales prices and production costs	1,295,956	(1,480,573)	(339,098)
Net changes in sales prices and production costs	(365,477)	(104,518)	(217,186)
Net change due to revisions in quantity estimates	132,900	(104,158)	(83,580)
Net change due to extensions, discoveries and improved recovery	383,308	14,645	324,755
Net change due to (divestiture) acquisition	0	0	(559,132)
Development costs incurred during the period	625,824	333,640	463,401
Difference in previously estimated development costs compared to actual costs incurred during the period	(123,976)	(96,749)	154,137
Changes in estimated future development costs	(486,518)	(153,104)	155,619
Net change in future income taxes	(578,951)	619,045	130,746
Accretion of discount and other	61,539	(39,203)	56,698
Total discounted cash flow at end of period	1,680,811	736,206	1,747,181	1,660,821
Production costs	(7,105,962)	(4,823,670)	(5,262,635)
Development costs	(3,902,875)	(2,450,589)	(1,674,829)
Income tax expense	(4,025,626)	(1,711,251)	(2,989,435)
Future Net Cash Flows	6,568,131	2,792,040	4,877,499
Discounted to present value at a 10% annual rate	(4,887,320)	(2,055,834)	(3,130,318)
Total standardized measure of discounted net cash flows	$ 1,680,811	$ 736,206	$ 1,747,181