Stockholders Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	$ 1,351,367	$ 1,382,677	$ 1,244,960	$ 1,270,528	$ 1,382,677	$ 1,270,528
Comprehensive income	49,082	(25,520)	17,611	(4,456)	23,562	13,155
Dividends declared	(8,090)	(8,104)	(8,072)	(8,133)
Common stock repurchases	(5,229)			(15,550)
Employee stock plans	3,263	2,314	3,207	2,571
Balance at end of period	$ 1,390,393	$ 1,351,367	$ 1,257,706	$ 1,244,960	$ 1,390,393	$ 1,257,706
Dividends declared (in dollars per share)	$ 0.16	$ 0.16	$ 0.16	$ 0.16
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period (in shares)	64,183	64,171	63,890	63,873	64,171	63,873
Balance at beginning of period	$ 642	$ 642	$ 639	$ 639	$ 642	$ 639
Employee stock plans (in shares)	17	12	14	17
Employee stock plans			$ 0	$ 0
Balance at end of period (in shares)	64,200	64,183	63,904	63,890	64,200	63,904
Balance at end of period	$ 642	$ 642	$ 639	$ 639	$ 642	$ 639
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	503,937	501,531	492,025	489,282	501,531	489,282
Employee stock plans	3,417	2,406	3,394	2,743
Balance at end of period	$ 507,354	$ 503,937	$ 495,419	$ 492,025	$ 507,354	$ 495,419
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period (in shares)	13,531	13,530	13,449	13,051	13,530	13,051
Balance at beginning of period	$ (517,060)	$ (516,992)	$ (513,708)	$ (498,074)	$ (516,992)	$ (498,074)
Common stock repurchases (in shares)	100			396
Common stock repurchases	$ (5,229)			$ (15,550)
Employee stock plans (in shares)	3	1	1	2
Employee stock plans	$ (123)	$ (68)	$ (53)	$ (84)
Balance at end of period (in shares)	13,634	13,531	13,450	13,449	13,634	13,450
Balance at end of period	$ (522,412)	$ (517,060)	$ (513,761)	$ (513,708)	$ (522,412)	$ (513,761)
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	1,531,065	1,519,811	1,510,688	1,489,176	1,519,811	1,489,176
Comprehensive income	24,491	19,382	567	29,733
Dividends declared	(8,090)	(8,104)	(8,072)	(8,133)
Employee stock plans	(31)	(24)	(134)	(88)
Balance at end of period	1,547,435	1,531,065	1,503,049	1,510,688	1,547,435	1,503,049
Accumulated Other Non-Owner Changes to Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(167,217)	(122,315)	(244,684)	(210,495)	(122,315)	(210,495)
Comprehensive income	24,591	(44,902)	17,044	(34,189)
Balance at end of period	$ (142,626)	$ (167,217)	$ (227,640)	$ (244,684)	$ (142,626)	$ (227,640)