Supplemental Gas Data PV-10 Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014 MMcf	Dec. 31, 2013 MMcf	Dec. 31, 2012 MMcf	Dec. 31, 2011 MMcf
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Beginning reserves	6,827,616,000	5,731,214,000	3,993,458,000	3,480,027,000
Revenues	$ 28,502,852	$ 21,602,594	$ 11,777,550
Net changes in sales prices and production costs	517,731	1,295,956	(1,480,573)
Net changes in sales prices and production costs	(559,563)	(365,477)	(104,518)
Net change due to revisions in quantity estimates	151,233	132,900	(104,158)
Net change due to extensions, discoveries and improved recovery	418,775	383,308	14,645
Development costs incurred during the period	952,733	625,824	333,640
Difference in previously estimated development costs compared to actual costs incurred during the period	(102,949)	(123,976)	(96,749)
Changes in estimated future development costs	595,221	(486,518)	(153,104)
Net change in future income taxes	(798,470)	(578,951)	619,045
Accretion of discount and other	128,636us-gaap_AccretionOfDiscount	61,539us-gaap_AccretionOfDiscount	(39,203)us-gaap_AccretionOfDiscount
Total discounted cash flow at end of period	2,984,158	1,680,811	736,206	1,747,181
Production costs	(10,100,868)	(7,105,962)	(4,823,670)
Development costs	(3,368,621)	(3,902,875)	(2,450,589)
Income tax expense	(5,711,989)	(4,025,626)	(1,711,251)
Future Net Cash Flows	9,321,374	6,568,131	2,792,040
Discounted to present value at a 10% annual rate	(6,337,216)	(4,887,320)	(2,055,834)
Total standardized measure of discounted net cash flows	$ 2,984,158	$ 1,680,811	$ 736,206
Natural Gas [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Beginning reserves	6,317,600,000	5,585,107,000	3,905,437,000	3,470,551,000

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Amount of estimated future cash inflows from sale of proved oil and gas reserves.

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Amount of estimated future cost to be incurred in developing proved oil and gas reserves.

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Amount of estimated future income tax expense to be incurred based on the future income less future expense derived from production and sale of proved oil and gas reserves.

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Amount of estimated net future cash inflows, after subtracting future development and production costs and future income tax expenses, from sale of proved oil and gas reserves.

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Amount of increase (decrease) in standardized measure of discounted future net cash flow as a result of change in sales and transfer prices and in production (lifting) costs related to future production.

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The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.

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Amount of (increase) decrease in standardized measure of discounted future net cash flow as a result of sales and transfers of oil and gas produced.

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