Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated Other Comprehensive Income (Loss)	Retained earnings
Balance at Dec. 31, 2012	$ 3,163,699	$ 3,712	$ 1,224,979		$ 1,935,008
Balance, shares at Dec. 31, 2012		371,209,362
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	764,219				764,219
Other Comprehensive Income (Loss), Net of Tax	0
Stock-based compensation	39,886		39,886
Restricted stock:
Issued	5	$ 5	0
Issued, shares		522,518
Repurchased and canceled	(14,690)	$ (3)	(14,687)
Repurchased and canceled, shares		(277,050)
Forfeited	(1)	$ (1)
Forfeited, shares		(137,512)
Balance at Dec. 31, 2013	3,953,118	$ 3,713	1,250,178		2,699,227
Balance, shares at Dec. 31, 2013		371,317,318
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	977,341				977,341
Other Comprehensive Income (Loss), Net of Tax	(385)			$ (385)
Stock-based compensation	54,343		54,343
Restricted stock:
Issued	14	$ 14	0
Issued, shares		1,424,764
Repurchased and canceled	(16,583)	$ (3)	(16,580)
Repurchased and canceled, shares		(283,434)
Forfeited	(4)	$ (4)
Forfeited, shares		(453,146)
Balance at Dec. 31, 2014	$ 4,967,844	$ 3,720	1,287,941	(385)	3,676,568
Balance, shares at Dec. 31, 2014	372,005,502	372,005,502
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ (353,668)				(353,668)
Other Comprehensive Income (Loss), Net of Tax	(2,969)			(2,969)
Stock-based compensation	51,817		51,817
Excess Tax Benefit from Share-based Compensation	13,177		13,177
Restricted stock:
Issued	15	$ 15	0
Issued, shares		1,462,534
Repurchased and canceled	(7,313)	$ (2)	(7,311)
Repurchased and canceled, shares		(172,786)
Forfeited	(3)	$ (3)
Forfeited, shares		(336,170)
Balance at Dec. 31, 2015	$ 4,668,900	$ 3,730	$ 1,345,624	$ (3,354)	$ 3,322,900
Balance, shares at Dec. 31, 2015	372,959,080	372,959,080