Quarterly Financial Data - Schedule Of Quarterly Financial Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 820,334	[1]	$ 823,835	[1]	$ 1,100,752	[1]	$ 710,229	[1]	$ 688,972	[1]	$ 483,729	[1]	$ 1,004,719	[1]	$ 395,100	[1]	$ 3,455,150	$ 2,572,520	$ 1,649,789
Gain (loss) on derivative instruments, net	(102,202)	[1]	(203,774)	[1]	199,056	[1]	(84,831)	[1]	9,639	[1]	(158,294)	[1]	471,728	[1]	(169,057)	[1]	(191,751)	154,016	(30,049)
Income from operations	273,706		328,043		573,872		270,146		365,220		105,522		686,474		135,591		1,445,767	1,292,807	760,752
Net income	$ 132,824		$ 167,498		$ 323,270		$ 140,627		$ 220,511		$ 44,096		$ 405,684		$ 69,094		$ 764,219	$ 739,385	$ 429,072
Net income per share: Basic	$ 0.72		$ 0.91		$ 1.76		$ 0.76		$ 1.20		$ 0.24		$ 2.26		$ 0.38		$ 4.15	$ 4.08	$ 2.42
Net income per share: Diluted	$ 0.72		$ 0.91		$ 1.75		$ 0.76		$ 1.19		$ 0.24		$ 2.25		$ 0.38		$ 4.13	$ 4.07	$ 2.41

[1] Gains and losses on mark-to-market derivative instruments are reflected in “Total revenues” on both the consolidated statements of income and this table of unaudited quarterly financial data. Derivative gains and losses have been shown separately to illustrate the fluctuations in revenues that are attributable to the Company’s derivative instruments. Commodity price fluctuations each quarter can result in significant swings in mark-to-market gains and losses, which affects comparability between periods.