Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	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, 2011	$ 722,400	$ 586	$ 316,251	$ (79,569)	$ 560,186	$ (75,054)
Balance (in shares) at Dec. 31, 2011		58,594,000		4,254,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	103,551				95,249	8,302
Dividends paid	(21,662)				(21,662)
Common stock repurchases	(19,037)			(19,037)
Common stock repurchases (in shares)				700,000
Employee stock plans		6
Employee stock plans (in shares)		608,227
Employee stock plans, other			16,337
Employee stock plans, shares withheld for taxes (in shares)				46,000
Employee stock plans, shares withheld for taxes				(1,150)
Dividends paid to holders of certain restricted stock units					(327)
Employee stock plans, total	14,866
Balance at Dec. 31, 2012	800,118	592	332,588	(99,756)	633,446	(66,752)
Balance (in shares) at Dec. 31, 2012		59,202,000		5,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	363,223				270,527	92,696
Dividends paid	(22,422)				(22,422)
Common stock repurchases	(68,608)			(68,608)
Common stock repurchases (in shares)				2,350,697
Männer Acquisition (in shares)				(1,032,000)
Männer Acquisition	36,695		22,890	13,805
Employee stock plans		11
Employee stock plans (in shares)		1,104,099
Employee stock plans, other			34,869
Employee stock plans, shares withheld for taxes (in shares)				70,000
Employee stock plans, shares withheld for taxes				(2,090)
Dividends paid to holders of certain restricted stock units					(382)
Employee stock plans, total	32,408
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
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
Convertible debt redemption, net of tax	(8,666)		(8,666)
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