Consolidated Statements Of Shareholders' Equity - 9 months ended Sep. 30, 2018 - 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, 2017	49,143	49,143
Balances, value at Dec. 31, 2017	$ 1,339,138	$ 4,914	$ 634,192	$ 708,181	$ (8,149)
Stock-based compensation expense	$ 8,229	$ 0	8,229	0	0
Shares repurchased and retired, shares	(4,401)	(4,401)
Shares repurchased and retired, value	$ (122,053)	$ (440)	(48,913)	(72,700)	0
Stock options exercised, shares	187	187
Stock options exercised, value	$ 3,463	$ 19	3,444	0	0
Vesting of restricted stock units, shares	229	229
Vesting of restricted stock units, value	$ 0	$ 23	(23)	0	0
Shares withheld for taxes, shares	(28)	(28)
Shares withheld for taxes, value	$ (822)	$ (3)	(819)	0	0
Dividends declared	(21,005)	0	0	(21,005)	0
Net loss	(4,899)	0	0	(4,899)	0
Other comprehensive loss	$ (369)	$ 0	0	0	(369)
Balances, shares at Sep. 30, 2018	45,130	45,130
Balances, value at Sep. 30, 2018	$ 1,201,682	$ 4,513	$ 596,110	$ 609,577	$ (8,518)