Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock, at Cost [Member]
Beginning balance, Shares at Dec. 31, 2015		191,368,727
Issuance of shares under equity-based compensation plans, shares		1,615,810
Shares surrendered under equity-based compensation plans		(115,598)
Ending balance, Shares at Sep. 30, 2016		192,868,939
Beginning balance at Dec. 31, 2015		$ 1,923	$ 2,216,202	$ (812,394)	$ (171,678)	$ (11,333)
Issuance of shares under equity-based compensation plans		17	8,620
Equity-based compensation			26,530
Tax benefit from shares issued under equity-based compensation plans			7,517
Net income	$ 168,372			168,372
Other comprehensive income, net of tax	2,401				2,401
Net shares surrendered under equity-based compensation plans						(2,946)
Ending balance at Sep. 30, 2016	1,433,231	$ 1,940	2,258,869	(644,022)	(169,277)	(14,279)
Ending balance, Shares at Sep. 30, 2016		192,868,939
Net income	93,831
Other comprehensive income, net of tax	7,977
Ending balance at Sep. 30, 2016	$ 1,433,231	$ 1,940	2,258,869	(644,022)	(169,277)	(14,279)
Beginning balance, Shares at Dec. 31, 2016	193,837,437	193,837,437
Repurchase of common stock	(2,500,000)
Beginning balance at Dec. 31, 2016	$ 1,394,084	$ 1,950	2,282,014	(589,556)	(285,113)	(15,211)
Repurchase of common stock	$ (100,000)
Beginning balance, Shares at Dec. 31, 2016	193,837,437	193,837,437
Issuance of shares under equity-based compensation plans, shares		2,117,965
Shares surrendered under equity-based compensation plans		(398,698)
Repurchase of common stock		(4,794,990)
Ending balance, Shares at Sep. 30, 2017	190,761,714	190,761,714
Beginning balance at Dec. 31, 2016	$ 1,394,084	$ 1,950	2,282,014	(589,556)	(285,113)	(15,211)
Issuance of shares under equity-based compensation plans		21	8,782
Equity-based compensation			31,656
Cumulative effect of change in accounting principle			295
Net income	140,183			140,183
Cumulative effect of change in accounting principle				(206)
Other comprehensive income, net of tax	165,775				165,775
Repurchase of common stock						(175,000)
Net shares surrendered under equity-based compensation plans						(14,956)
Ending balance at Sep. 30, 2017	$ 1,550,634	$ 1,971	2,322,747	(449,579)	(119,338)	(205,167)
Ending balance, Shares at Sep. 30, 2017	190,761,714	190,761,714
Net income	$ 51,157
Other comprehensive income, net of tax	43,578
Ending balance at Sep. 30, 2017	$ 1,550,634	$ 1,971	$ 2,322,747	$ (449,579)	$ (119,338)	$ (205,167)