Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Total
Balance at Dec. 31, 2013	$ 1,257	$ 604,330	$ 414,947	$ 2,550	$ 1,023,084
Balance, Shares at Dec. 31, 2013	125,690,240
Net income			126,333		126,333
Other comprehensive income (loss), net of tax				(14,214)	(14,214)
Issuance of common stock under employee plans, including tax benefits	$ 21	31,254			31,275
Issuance of common stock under employee plans, including tax benefits, shares	2,159,031
Stock-based compensation		26,242			26,242
Dividends paid			(76,287)		(76,287)
Disqualified dispositions		1,063			1,063
Balance at Dec. 31, 2014	$ 1,278	662,889	464,993	(11,664)	1,117,496
Balance, Shares at Dec. 31, 2014	127,849,271
Net income			95,262		95,262
Other comprehensive income (loss), net of tax				(26,426)	(26,426)
Issuance of common stock under employee plans, including tax benefits	$ 18	27,767			27,785
Issuance of common stock under employee plans, including tax benefits, shares	1,846,070
Stock-based compensation		25,891			25,891
Business acquisition	$ 4	13,774			13,778
Business acquisition, shares	367,481
Repurchase of common stock	$ (25)	(13,449)	(61,781)		(75,255)
Repurchase of common stock, shares	(2,591,218)
Dividends paid			(97,643)		(97,643)
Disqualified dispositions		833			833
Balance at Dec. 31, 2015	$ 1,275	717,705	400,831	(38,090)	$ 1,081,721
Balance, Shares at Dec. 31, 2015	127,471,604				127,471,604
Net income			82,734		$ 82,734
Other comprehensive income (loss), net of tax				3,469	3,469
Issuance of common stock under employee plans, including tax benefits	$ 19	28,888			28,907
Issuance of common stock under employee plans, including tax benefits, shares	1,894,151
Stock-based compensation		25,920			25,920
Business acquisition, shares	44,004
Repurchase of common stock	$ (2)	(1,167)	(4,466)		(5,635)
Repurchase of common stock, shares	(206,780)
Dividends paid			(102,897)		(102,897)
Balance at Dec. 31, 2016	$ 1,292	$ 771,346	$ 376,202	$ (34,621)	$ 1,114,219
Balance, Shares at Dec. 31, 2016	129,202,979				129,202,979