Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Crude oil and natural gas sales	$ 2,315,840	$ 1,553,629	$ 917,503
Crude oil and natural gas sales to affiliates	63,593	93,790	31,021
Gain (loss) on derivative instruments, net	154,016	(30,049)	(130,762)
Crude oil and natural gas service operations	39,071	32,419	21,303
Total revenues	2,572,520	1,649,789	839,065
Operating costs and expenses:
Production expenses	193,466	135,178	86,557
Production and other expenses to affiliates	6,675	4,632	6,646
Production taxes and other expenses	223,737	143,236	76,659
Exploration expenses	23,507	27,920	12,763
Crude oil and natural gas service operations	32,248	26,735	18,065
Depreciation, depletion, amortization and accretion	692,118	390,899	243,601
Property impairments	122,274	108,458	64,951
General and administrative expenses	121,735	72,817	49,090
Gain on sale of assets, net	(136,047)	(20,838)	(29,588)
Total operating costs and expenses	1,279,713	889,037	528,744
Income from operations	1,292,807	760,752	310,321
Other income (expense):
Interest expense	(140,708)	(76,722)	(53,147)
Other	3,097	3,415	1,293
Total other income (expense)	(137,611)	(73,307)	(51,854)
Income before income taxes	1,155,196	687,445	258,467
Provision for income taxes	415,811	258,373	90,212
Net income	$ 739,385	$ 429,072	$ 168,255
Basic net income per share	$ 4.08	$ 2.42	$ 1.00
Diluted net income per share	$ 4.07	$ 2.41	$ 0.99