Consolidated Statements Of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]
Balances, shares at Dec. 31, 2012	55,186
Balances, value at Dec. 31, 2012	$ 1,139,525	$ 5,519	$ 651,148	$ 493,666	$ (10,536)	$ (272)
Stock-based compensation expense	$ 6,267		6,267
Shares repurchased and retired, shares	(2,093)
Shares repurchased and retired, value	$ (41,168)	(209)	(22,556)	(18,403)
Stock options exercised, shares	713
Stock options exercised, value	$ 11,203	71	11,132
Vesting of restricted stock units, net restricted share forfeitures, shares	27
Vesting of restricted stock units, net of restricted share forfeitures, value		3	(3)
Shares withheld for taxes, shares	(8)
Shares withheld for taxes, value	$ (142)	(1)	(141)
Excess tax benefit (shortfall) of stock-based compensation	(1,253)		(1,253)
Comprehensive income	$ 112,387			110,945	1,442
Balances, shares at Dec. 31, 2013	53,825
Balances, value at Dec. 31, 2013	$ 1,226,819	5,383	644,594	586,208	(9,094)	(272)
Stock-based compensation expense	$ 7,213		7,213
Shares repurchased and retired, shares	(1,861)
Shares repurchased and retired, value	$ (43,800)	(186)	(20,250)	(23,364)
Stock options exercised, shares	940
Stock options exercised, value	$ 18,867	94	18,773
Vesting of restricted stock units, net restricted share forfeitures, shares	103
Vesting of restricted stock units, net of restricted share forfeitures, value		10	(10)
Shares withheld for taxes, shares	(13)
Shares withheld for taxes, value	$ (309)	(1)	(308)
Excess tax benefit (shortfall) of stock-based compensation	(25)		(25)
Cancellation of treasury shares			(272)			272
Comprehensive income	$ 80,860			81,241	(381)
Balances, shares at Dec. 31, 2014	52,994
Balances, value at Dec. 31, 2014	$ 1,289,625	5,300	649,715	644,085	(9,475)	0
Stock-based compensation expense	$ 7,709		7,709
Shares repurchased and retired, shares	(3,066)
Shares repurchased and retired, value	$ (68,365)	(307)	(33,477)	(34,581)
Stock options exercised, shares	114
Stock options exercised, value	$ 1,976	11	1,965
Vesting of restricted stock units, net restricted share forfeitures, shares	160
Vesting of restricted stock units, net of restricted share forfeitures, value		16	(16)
Shares withheld for taxes, shares	(24)
Shares withheld for taxes, value	$ (571)	(2)	(569)
Excess tax benefit (shortfall) of stock-based compensation	(330)		(330)
Comprehensive income	$ 91,860			95,401	(3,541)
Balances, shares at Dec. 31, 2015	50,178
Balances, value at Dec. 31, 2015	$ 1,321,904	$ 5,018	$ 624,997	$ 704,905	$ (13,016)	$ 0