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, 2012	$ 690,530	$ 686	$ 268,515	$ 409,091	$ 12,238
Beginning Balance (in shares) at Dec. 31, 2012		68,647
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	57,893	$ 3	57,890
Deferred compensation	(8,421)		(4,358)	(4,063)
Employee stock compensation (in shares)		264
Proceeds from stock issuances under employee plans	26,922	$ 10	26,912
Proceeds from stock issuances under employee plans (in shares)		1,049
Tax effect of exercise of stock options	28,621		28,621
Cash dividends declared ($2.12 per share, $1.92 per share and $1.68 per share in 2014, 2013, and 2012 respectively)	(113,722)			(113,722)
Repurchase and retirement of common shares	$ (530,033)	$ (43)	(16,964)	(513,026)
Repurchase and retirement of common shares (in shares)	(4,337)	(4,337)
Net income	$ 377,292			377,292
Other comprehensive income	6,523				6,523
Ending Balance at Dec. 31, 2013	535,605	$ 656	360,616	155,572	18,761
Ending 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 ($2.12 per share, $1.92 per share and $1.68 per share in 2014, 2013, and 2012 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 ($2.12 per share, $1.92 per share and $1.68 per share in 2014, 2013, and 2012 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