Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Retained Earnings	Accumulated Other Non-Owner Changes to Equity
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		8,890,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	153,844				59,415	94,429
Dividends paid	(29,551)				(29,551)
Common stock repurchases (in shares)				677,100
Common stock repurchases	(40,791)			$ (40,791)
Employee stock plans	8,461	$ 3	14,130	$ (5,380)	(292)
Employee stock plans (in shares)		341,837		89,000
Balance at Dec. 31, 2017	1,260,321	$ 630	457,365	$ (297,998)	1,206,723	(106,399)
Balance (in shares) at Dec. 31, 2017		63,034,000		9,656,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	101,416				166,186	(64,770)
Dividends paid	(32,206)				(32,206)
Reclassification pursuant to accounting guidance related to U.S. Tax Reform (Note 1)	0				19,331	(19,331)
Cumulative effect of change in Revenue Recognition accounting guidance (Note 1)	4,295				4,295
Common stock repurchases (in shares)				2,292,100
Common stock repurchases	(138,275)			$ (138,275)
Employee stock plans	7,505	$ 4	13,453	$ (5,395)	(557)
Employee stock plans (in shares)		332,893		86,000
Balance at Dec. 31, 2018	1,203,056	$ 634	470,818	$ (441,668)	1,363,772	(190,500)
Balance (in shares) at Dec. 31, 2018		63,367,000		12,034,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	138,355				158,350	(19,995)
Dividends paid	(32,544)				(32,544)
Common stock repurchases (in shares)				900,000
Common stock repurchases	(50,347)			$ (50,347)
Employee stock plans	12,008	$ 5	18,464	$ (6,059)	(402)
Employee stock plans (in shares)		505,623		117,000
Balance at Dec. 31, 2019	$ 1,270,528	$ 639	$ 489,282	$ (498,074)	$ 1,489,176	$ (210,495)
Balance (in shares) at Dec. 31, 2019		63,873,000		13,051,000