Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Non-Owner Changes to Equity [Member]
Balance at Dec. 31, 2013	$ 1,141,414	$ 603	$ 390,347	$ (156,649)	$ 881,169	$ 25,944
Balance (in shares) at Dec. 31, 2013		60,306,000		6,389,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	(7,027)				118,370	(125,397)
Dividends paid	(24,464)				(24,464)
Common stock repurchases	(8,389)			$ (8,389)
Common stock repurchases (in shares)				220,794
Convertible debt redemption, net of tax	(8,666)		(8,666)	$ 0
Employee stock plans		$ 9
Employee stock plans (in shares)		923,852
Employee stock plans, other			23,844
Employee stock plans, shares withheld for taxes (in shares)				119,000
Employee stock plans, shares withheld for taxes				$ (4,367)
Dividends paid to holders of certain restricted stock units					(561)
Employee stock plans, total	18,925
Balance at Dec. 31, 2014	1,111,793	$ 612	405,525	$ (169,405)	974,514	(99,453)
Balance (in shares) at Dec. 31, 2014		61,230,000		6,729,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	77,581				121,380	(43,799)
Dividends paid	(26,176)				(26,176)
Common stock repurchases	(52,103)			$ (52,103)
Common stock repurchases (in shares)				1,352,596
Employee stock plans		$ 9
Employee stock plans (in shares)		841,164
Employee stock plans, other			22,033
Employee stock plans, shares withheld for taxes (in shares)				125,000
Employee stock plans, shares withheld for taxes				$ (4,913)
Dividends paid to holders of certain restricted stock units					(471)
Employee stock plans, total	16,658
Balance at Dec. 31, 2015	1,127,753	$ 621	427,558	$ (226,421)	1,069,247	(143,252)
Balance (in shares) at Dec. 31, 2015		62,071,000		8,207,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	78,025				135,601	(57,576)
Dividends paid	(27,435)				(27,435)
Common stock repurchases	(20,520)			$ (20,520)
Cumulative effect of change in accounting guidance (Note 12)	198				198
Common stock repurchases (in shares)				550,994
Employee stock plans		$ 6
Employee stock plans (in shares)		621,259
Employee stock plans, other			15,677
Employee stock plans, shares withheld for taxes (in shares)				132,000
Employee stock plans, shares withheld for taxes				$ (4,886)
Dividends paid to holders of certain restricted stock units					(460)
Employee stock plans, total	10,337
Balance at Dec. 31, 2016	$ 1,168,358	$ 627	$ 443,235	$ (251,827)	$ 1,177,151	$ (200,828)
Balance (in shares) at Dec. 31, 2016		62,692,000		8,889,994.000