CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock
Beginning Balance at Dec. 31, 2013	$ 2,755,997	$ 1,865	$ 913,505	$ 2,707,439	$ 14,076	$ (880,888)
Beginning Balance (in shares) at Dec. 31, 2013		186,487,000
Net income (loss)	162,664			162,664
Foreign currency translation adjustment	(7,613)				(7,613)
Issuance of restricted stock		$ 11	(11)
Issuance of restricted stock (in shares)		1,102,000
Vesting of restricted stock units	1	$ 1
Vesting of restricted stock units (in shares)		10,000
Forfeitures of restricted stock		$ (1)	1
Forfeitures of restricted stock (in shares)		(61,000)
Exercise of stock options	35,435	$ 17	35,418
Exercise of stock options (in shares)		1,725,000
Stock-based compensation	27,032		27,032
Tax benefit (expense) related to stock-based compensation	8,729		8,729
Payment of cash dividends	(58,288)			(58,288)
Purchase of treasury stock	(18,147)					(18,147)
Ending Balance at Dec. 31, 2014	2,905,810	$ 1,893	984,674	2,811,815	6,463	(899,035)
Ending Balance (in shares) at Dec. 31, 2014		189,263,000
Net income (loss)	(294,486)			(294,486)
Foreign currency translation adjustment	(10,556)				(10,556)
Issuance of restricted stock		$ 12	(12)
Issuance of restricted stock (in shares)		1,180,000
Vesting of restricted stock units (in shares)		14,000
Forfeitures of restricted stock		$ (1)	1
Forfeitures of restricted stock (in shares)		(82,000)
Stock-based compensation	28,510		28,510
Tax benefit (expense) related to stock-based compensation	(1,362)		(1,362)
Payment of cash dividends	(58,775)			(58,775)
Purchase of treasury stock	(8,010)					(8,010)
Ending Balance at Dec. 31, 2015	$ 2,561,131	$ 1,904	1,011,811	2,458,554	(4,093)	(907,045)
Ending Balance (in shares) at Dec. 31, 2015	190,374,801	190,375,000
Net income (loss)	$ (318,634)			(318,634)
Foreign currency translation adjustment	2,959				2,959
Shares issued for acquisition	6,733	$ 3	6,730
Shares issued for acquisition (in shares)		354,000
Issuance of restricted stock		$ 8	(8)
Issuance of restricted stock (in shares)		785,000
Vesting of restricted stock units (in shares)		15,000
Forfeitures of restricted stock (in shares)		(43,000)
Exercise of stock options	$ 707		707
Exercise of stock options (in shares)	40,000	40,000
Stock-based compensation	$ 28,324		28,324
Tax benefit (expense) related to stock-based compensation	(4,868)		(4,868)
Payment of cash dividends	(23,579)			(23,579)
Purchase of treasury stock	(4,049)					(4,049)
Ending Balance at Dec. 31, 2016	$ 2,248,724	$ 1,915	$ 1,042,696	$ 2,116,341	$ (1,134)	$ (911,094)
Ending Balance (in shares) at Dec. 31, 2016	191,525,872	191,526,000