Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Gains (Losses) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2013	$ 4,637,258	$ 1,440	$ 1,988,720	$ 2,761,161	$ 350	$ (114,413)
Beginning Balance, shares at Dec. 31, 2013		143,952,248				4,916,800
Net (loss) income	387,011			387,011
Dividends to stockholders	(481,642)			(481,642)
Anti-dilution adjustment	(4,531)			(4,531)
Treasury stock purchase	$ (87,756)					$ (87,756)
Treasury stock purchase, shares	1,895,561					1,895,561
Stock options exercised	$ 213		213
Stock options exercised, shares		8,012
Stock-based compensation, net of tax	4,965		4,965
Net gain (loss) on derivative financial instruments	(3,861)				(3,861)
Net gain (loss) on investments	(94)				(94)
Ending Balance at Dec. 31, 2014	4,451,563	$ 1,440	1,993,898	2,661,999	(3,605)	$ (202,169)
Ending Balance, shares at Dec. 31, 2014		143,960,260				6,812,361
Net (loss) income	(274,285)			(274,285)
Dividends to stockholders	(68,578)			(68,578)
Stock-based compensation, net of tax			5,736
Stock-based compensation, vested shares issued (withheld), shares		18,617				7,810
Stock-based compensation, vested shares issued (withheld), value						$ (236)
Stock-based compensation expense, net of shares withheld for taxes	5,500
Net gain (loss) on derivative financial instruments	3,510				3,510
Net gain (loss) on investments	(4,940)				(4,940)
Ending Balance at Dec. 31, 2015	4,112,770	$ 1,440	1,999,634	2,319,136	(5,035)	$ (202,405)
Ending Balance, shares at Dec. 31, 2015		143,978,877				6,820,171
Net (loss) income	(372,503)			(372,503)
Anti-dilution adjustment	132			132
Stock-based compensation, net of tax			4,880
Stock-based compensation, vested shares issued (withheld), shares		18,880				7,923
Stock-based compensation, vested shares issued (withheld), value						$ (181)
Stock-based compensation expense, net of shares withheld for taxes	4,699
Net gain (loss) on derivative financial instruments	(5)				(5)
Net gain (loss) on investments	5,041				5,041
Ending Balance at Dec. 31, 2016	$ 3,750,134	$ 1,440	$ 2,004,514	$ 1,946,765	$ 1	$ (202,586)
Ending Balance, shares at Dec. 31, 2016		143,997,757				6,828,094