Consolidated Statements Of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated other Comprehensive Income (Loss)	Non Controlling Interest
Beginning Balance at Dec. 31, 2016	$ 867,040	$ 631	$ 650,162	$ 300,084	$ (83,837)
Beginning Balance (in shares) at Dec. 31, 2016		63,109
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	50,054	$ 1	50,053
Deferred compensation	(2,989)		(1,536)	4,525
Employee stock compensation (in shares)		60
Proceeds from stock issuances under employee plans	42,738	$ 9	42,729
Proceeds from stock issuances under employee plans (in shares)		934
Cash dividends declared ($2.32 per share, $2.20 per share and $2.12 per share in 2017, 2016, and 2015 respectively)	(145,423)			145,423
Repurchase and retirement of common shares	$ (90,461)	$ 10	10,586	79,865
Repurchase and retirement of common shares (in shares)	(1,028)	1,028
Net income	$ 172,492			172,492
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	172,492
Other comprehensive income	38,208				38,208
Ending Balance at Dec. 31, 2017	931,659	$ 631	733,894	242,763	(45,629)
Ending Balance (in shares) at Dec. 31, 2017		63,075
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	63,966	$ 2	63,964
Deferred compensation	4,880		(111)	(4,769)
Employee stock compensation (in shares)		245
Proceeds from stock issuances under employee plans	47,092	$ 8	47,084
Proceeds from stock issuances under employee plans (in shares)		754
Cash dividends declared ($2.32 per share, $2.20 per share and $2.12 per share in 2017, 2016, and 2015 respectively)	(149,032)			149,032
Repurchase and retirement of common shares	$ (348,663)	$ 32	37,066	311,565
Repurchase and retirement of common shares (in shares)	(3,184)	3,184
Cumulative effect of adoption of accounting standards (ASU 2018-02)	$ 1,079		1	1,078
Net income	335,257			335,257
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	335,257
Other comprehensive income	(17,344)				(17,344)
Ending Balance at Dec. 31, 2018	866,736
Ending Balance (in shares) at Dec. 31, 2018		60,890
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	867,015	$ 609	807,986	121,114	(62,973)	$ 279
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	74,962	$ 4	74,958
Deferred compensation	(6,761)		4,488	2,273
Employee stock compensation (in shares)		412
Proceeds from stock issuances under employee plans	15,660	$ 2	15,658
Proceeds from stock issuances under employee plans (in shares)		205
Cash dividends declared ($2.32 per share, $2.20 per share and $2.12 per share in 2017, 2016, and 2015 respectively)	(149,101)			149,101
Repurchase and retirement of common shares	$ (8,378)	$ 1	1,265	7,112
Repurchase and retirement of common shares (in shares)	(95)	95
Cumulative effect of adoption of accounting standards (ASU 2018-02)	$ 0			668	(668)
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	279
Net income	323,960
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	323,884			323,960		(76)
Other comprehensive income	(9,079)				(9,079)
Ending Balance at Dec. 31, 2019	1,107,999
Ending Balance (in shares) at Dec. 31, 2019		61,412
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 1,108,202	$ 614	$ 892,849	$ 287,256	$ (72,720)	$ 203