Consolidated Statements Of Shareholders' Equity - 9 months ended Sep. 30, 2016 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balances, shares at Dec. 31, 2015	50,178	50,178
Balances, value at Dec. 31, 2015	$ 1,321,904	$ 5,018	$ 624,997	$ 704,905	$ (13,016)
Stock-based compensation expense	$ 4,302	$ 0	4,302	0	0
Shares repurchased and retired, shares	(1,923)	(1,923)
Shares repurchased and retired, value	$ (40,862)	$ (193)	(21,010)	(19,659)	0
Stock options exercised, shares	328	328
Stock options exercised, value	$ 5,544	$ 33	5,511	0	0
Vesting of restricted stock units, shares	197	197
Vesting of restricted stock units, value	$ 0	$ 20	(20)	0	0
Shares withheld for taxes, shares	(26)	(26)
Shares withheld for taxes, value	$ (554)	$ (3)	(551)	0	0
Excess tax shortfall of stock-based compensation	(193)	0	(193)	0	0
Net income	45,479	0	0	45,479	0
Other comprehensive loss	$ (1,303)	$ 0	0	0	(1,303)
Balances, shares at Sep. 30, 2016	48,754	48,754
Balances, value at Sep. 30, 2016	$ 1,334,317	$ 4,875	$ 613,036	$ 730,725	$ (14,319)