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)
Beginning Balance at Dec. 31, 2013	$ 535,605	$ 656	$ 360,616	$ 155,572	$ 18,761
Beginning Balance (in shares) at Dec. 31, 2013		65,623
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	63,183	$ 3	63,180
Deferred compensation	(5,107)		(3,020)	(2,087)
Employee stock compensation (in shares)		254
Proceeds from stock issuances under employee plans	31,313	$ 10	31,303
Proceeds from stock issuances under employee plans (in shares)		984
Tax effect of exercise of stock options	36,966		36,966
Cash dividends declared ($2.20 per share, $2.12 per share and $1.92 per share in 2016, 2015, and 2014 respectively)	(126,908)			(126,908)
Repurchase and retirement of common shares	$ (81,812)	$ (6)	(3,040)	(78,766)
Repurchase and retirement of common shares (in shares)	(554)	(554)
Net income	$ 454,029			454,029
Other comprehensive income	(46,002)				(46,002)
Ending Balance at Dec. 31, 2014	861,267	$ 663	486,005	401,840	(27,241)
Ending Balance (in shares) at Dec. 31, 2014		66,307
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	61,929	$ 2	61,927
Deferred compensation	3,883		(2,994)	6,877
Employee stock compensation (in shares)		144
Proceeds from stock issuances under employee plans	32,535	$ 10	32,525
Proceeds from stock issuances under employee plans (in shares)		1,037
Tax effect of exercise of stock options	34,654		34,654
Cash dividends declared ($2.20 per share, $2.12 per share and $1.92 per share in 2016, 2015, and 2014 respectively)	(139,285)			(139,285)
Repurchase and retirement of common shares	$ (293,616)	$ (22)	(15,974)	(277,620)
Repurchase and retirement of common shares (in shares)	(2,179)	(2,179)
Net income	$ 455,361			455,361
Other comprehensive income	(35,251)				(35,251)
Ending Balance at Dec. 31, 2015	981,477	$ 653	596,143	447,173	(62,492)
Ending Balance (in shares) at Dec. 31, 2015		65,309
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	57,927	$ 3	57,924
Deferred compensation	917		1,379	(462)
Employee stock compensation (in shares)		303
Proceeds from stock issuances under employee plans	17,690	$ 4	17,686
Proceeds from stock issuances under employee plans (in shares)		405
Tax effect of exercise of stock options	3,578		3,578
Cash dividends declared ($2.20 per share, $2.12 per share and $1.92 per share in 2016, 2015, and 2014 respectively)	(140,336)			(140,336)
Repurchase and retirement of common shares	$ (245,816)	$ (29)	(26,548)	(219,239)
Repurchase and retirement of common shares (in shares)	(2,908)	(2,908)
Net income	$ 212,948			212,948
Other comprehensive income	(21,345)				(21,345)
Ending Balance at Dec. 31, 2016	$ 867,040	$ 631	$ 650,162	$ 300,084	$ (83,837)
Ending Balance (in shares) at Dec. 31, 2016		63,109