Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Treasury Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance (in shares) at Dec. 31, 2013		(17,795)
Beginning Balance at Dec. 31, 2013	$ 1,139,963	$ (305,750)	$ 45,376	$ 198,182	$ 1,202,219	$ (64)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends, $.1025, $.094 and $.086 per share in 2016, 2015 and 2014, respectively	(6,219)				(6,219)
Stock-Based Compensation (in shares)		17
Stock-Based Compensation	10,698	$ 300		10,398
Reissued Shares (in shares)		515
Reissued Shares	872	$ 7,162		(6,290)
Repurchased Shares (in shares)		(1,001)
Repurchased Shares	0	$ (25,000)		25,000
Net Earnings	78,233				78,233
Foreign Currency Translation Adjustment	(26)					(26)
Ending Balance (in shares) at Dec. 31, 2014		(18,264)
Ending Balance at Dec. 31, 2014	1,223,521	$ (323,288)	45,376	227,290	1,274,233	(90)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends, $.1025, $.094 and $.086 per share in 2016, 2015 and 2014, respectively	(6,822)				(6,822)
Stock-Based Compensation (in shares)		5
Stock-Based Compensation	13,694	$ 89		13,605
Reissued Shares (in shares)		107
Reissued Shares	943	$ 1,726		(783)
Net Earnings	135,709				135,709
Foreign Currency Translation Adjustment	(427)					(427)
Ending Balance (in shares) at Dec. 31, 2015		(18,152)
Ending Balance at Dec. 31, 2015	1,366,618	$ (321,473)	45,376	240,112	1,403,120	(517)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends, $.1025, $.094 and $.086 per share in 2016, 2015 and 2014, respectively	(7,420)				(7,420)
Stock-Based Compensation (in shares)		4
Stock-Based Compensation	20,228	$ 68		20,160
Reissued Shares (in shares)		217
Reissued Shares	(2,572)	$ 3,188		(5,760)
Repurchased Shares (in shares)		(1,373)
Repurchased Shares	(34,525)	$ (34,525)		0
Net Earnings	139,283				139,283
Foreign Currency Translation Adjustment	(14)					(14)
Ending Balance (in shares) at Dec. 31, 2016		(19,304)
Ending Balance at Dec. 31, 2016	$ 1,481,598	$ (352,742)	$ 45,376	$ 254,512	$ 1,534,983	$ (531)