Consolidated Statements Of Shareholders' Equity - 6 months ended Jun. 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	$ 5,405	$ 0	5,405	0	0
Shares repurchased and retired, shares	(2,174)	(2,174)
Shares repurchased and retired, value	$ (75,868)	$ (217)	(34,183)	(41,468)	0
Stock options exercised, shares	182	182
Stock options exercised, value	$ 3,377	$ 18	3,359	0	0
Vesting of restricted stock units, shares	209	209
Vesting of restricted stock units, value	$ 0	$ 21	(21)	0	0
Shares withheld for taxes, shares	(26)	(26)
Shares withheld for taxes, value	$ (771)	$ (3)	(768)	0	0
Dividends declared	(14,236)	0	0	(14,236)	0
Net loss	(12,698)	0	0	(12,698)	0
Other comprehensive loss	$ (202)	$ 0	0	0	(202)
Balances, shares at Jun. 30, 2018	47,334	47,334
Balances, value at Jun. 30, 2018	$ 1,244,145	$ 4,733	$ 607,984	$ 639,779	$ (8,351)