Consolidated Statements Of Shareholders' Equity - 6 months ended Jun. 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	$ 4,505	$ 0	4,505	0	0
Shares repurchased and retired, shares	(61)	(61)
Shares repurchased and retired, value	$ (2,000)	$ (6)	(672)	(1,322)	0
Stock options exercised, shares	411	411
Stock options exercised, value	$ 8,094	$ 41	8,053	0	0
Vesting of restricted stock units, shares	177	177
Vesting of restricted stock units, value	$ 0	$ 18	(18)	0	0
Shares withheld for taxes, shares	(12)	(12)
Shares withheld for taxes, value	$ (379)	$ (1)	(378)	0	0
Net income	26,863	0	0	26,863	0
Other comprehensive income	$ 3,289	$ 0	0	0	3,289
Balances, shares at Jun. 30, 2017	49,845	49,845
Balances, value at Jun. 30, 2017	$ 1,405,837	$ 4,985	$ 637,796	$ 773,943	$ (10,887)