Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]
Beginning Balance (in shares) at Dec. 31, 2014		63,203,000
Beginning Balance at Dec. 31, 2014	$ 709,956	$ 876	$ 225,449	$ 1,313,521	$ (165,624)	$ (664,266)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	172,413			172,413
Other comprehensive income (loss)	(43,182)				(43,182)
Dividends declared on common stock	(39,741)			(39,741)
Stock compensation expense	12,403		12,403
Net issuance of treasury stock for vested restricted stock units (in shares)		96,000
Net issuance of treasury stock for vested restricted stock units, including tax benefit	(2,533)		(561)			(1,972)
Repurchases of common stock (in shares)		(2,906,000)
Repurchases of common stock	(170,132)					(170,132)
Ending Balance at Dec. 31, 2015	639,184	$ 876	237,291	1,446,193	(208,806)	(836,370)
Ending Balance (in shares) at Dec. 31, 2015		60,393,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	153,351			153,351
Other comprehensive income (loss)	(15,050)				(15,050)
Dividends declared on common stock	(40,877)			(40,877)
Stock compensation expense	13,018		13,018
Adoption of accounting standard update related to stock compensation accounting	525		598	(73)
Net issuance of treasury stock for vested restricted stock units (in shares)		114,000
Net issuance of treasury stock for vested restricted stock units, including tax benefit	(3,430)		(1,144)			(2,286)
Repurchases of common stock (in shares)		(5,456,000)
Repurchases of common stock	(277,306)					(277,306)
Ending Balance at Dec. 31, 2016	$ 469,415	$ 876	249,763	1,558,594	(223,856)	(1,115,962)
Ending Balance (in shares) at Dec. 31, 2016	55,051,158	55,051,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 269,659			269,659
Other comprehensive income (loss)	56,968				56,968
Dividends declared on common stock	(40,493)			(40,493)
Stock compensation expense	14,639		14,639
Net issuance of treasury stock for vested restricted stock units (in shares)		192,000
Net issuance of treasury stock for vested restricted stock units, including tax benefit	(4,123)		(1,326)			(2,797)
Stock Issued During Period, Shares, Stock Splits		55,142,000
Adjustments to Additional Paid in Capital, Stock Split		$ 875	(875)
Adoption of accounting standards update related to reclassification of certain tax effects				22,085	(22,085)
Ending Balance at Dec. 31, 2017	$ 766,065	$ 1,751	$ 262,201	$ 1,809,845	$ (188,973)	$ (1,118,759)
Ending Balance (in shares) at Dec. 31, 2017	110,385,344	110,385,000