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, 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, shares	103
Vesting of restricted stock units, value		10	(10)
Shares withheld for taxes, shares	(13)
Shares withheld for taxes, value	$ (309)	(1)	(308)
Excess tax shortfall of stock-based compensation	(25)		(25)
Cancellation of treasury shares	0		(272)			272
Net income	81,241			81,241
Other comprehensive loss	$ (381)				(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, shares	160
Vesting of restricted stock units, value		16	(16)
Shares withheld for taxes, shares	(24)
Shares withheld for taxes, value	$ (571)	(2)	(569)
Excess tax shortfall of stock-based compensation	(330)		(330)
Net income	95,401			95,401
Other comprehensive loss	$ (3,541)				(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
Stock-based compensation expense	$ 5,322		5,322
Shares repurchased and retired, shares	(1,959)
Shares repurchased and retired, value	$ (41,929)	(196)	(21,396)	(20,337)
Stock options exercised, shares	928
Stock options exercised, value	$ 18,825	93	18,732
Vesting of restricted stock units, shares	209
Vesting of restricted stock units, value		21	(21)
Shares withheld for taxes, shares	(26)
Shares withheld for taxes, value	$ (568)	(3)	(565)
Excess tax shortfall of stock-based compensation	(976)		(976)
Net income	64,047			64,047
Other comprehensive loss	$ (1,160)				(1,160)
Balances, shares at Dec. 31, 2016	49,330
Balances, value at Dec. 31, 2016	$ 1,365,465	$ 4,933	$ 626,093	$ 748,615	$ (14,176)	$ 0