Consolidated Statements Of Shareholders' Equity - 9 months ended Sep. 30, 2017 - 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, 2016	49,330	49,330
Balances, value at Dec. 31, 2016	$ 1,365,465	$ 4,933	$ 626,306	$ 748,402	$ (14,176)
Stock-based compensation expense	$ 6,819	$ 0	6,819	0	0
Shares repurchased and retired, shares	(183)	(183)
Shares repurchased and retired, value	$ (5,887)	$ (18)	(2,031)	(3,838)	0
Stock options exercised, shares	502	502
Stock options exercised, value	$ 9,828	$ 50	9,778	0	0
Vesting of restricted stock units, shares	185	185
Vesting of restricted stock units, value	$ 0	$ 18	(18)	0	0
Shares withheld for taxes, shares	(12)	(12)
Shares withheld for taxes, value	$ (383)	$ (1)	(382)	0	0
Net income	44,375	0	0	44,375	0
Other comprehensive loss	$ 4,694	$ 0	0	0	4,694
Balances, shares at Sep. 30, 2017	49,822	49,822
Balances, value at Sep. 30, 2017	$ 1,424,911	$ 4,982	$ 640,472	$ 788,939	$ (9,482)