Consolidated Statements Of Shareholders' Equity - 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
Balances, value at Dec. 31, 2015	$ 1,332,273	$ 5,018	$ 624,997	$ 715,274	$ (13,016)
Stock-based compensation expense	$ 5,322	0	5,322	0	0
Shares repurchased and retired, shares	(1,959)
Shares repurchased and retired, value	$ (41,929)	(196)	(21,396)	(20,337)	0
Stock options exercised, shares	928
Stock options exercised, value	$ 18,825	93	18,732	0	0
Vesting of restricted stock units, shares	209
Vesting of restricted stock units, value	$ 0	21	(21)	0	0
Shares withheld for taxes, shares	(26)
Shares withheld for taxes, value	$ (568)	(3)	(565)	0	0
Excess tax shortfall of stock-based compensation	(976)	0	(976)	0	0
Net income (loss)	63,933	0	0	63,933	0
Other comprehensive loss	$ (1,160)	0	0	0	(1,160)
Balances, shares at Dec. 31, 2016	49,330
Balances, value at Dec. 31, 2016	$ 1,375,720	4,933	626,093	758,870	(14,176)
Cumulative effect of accounting change	0	0	213	(213)	0
Stock-based compensation expense	$ 7,815	0	7,815	0	0
Shares repurchased and retired, shares	(963)
Shares repurchased and retired, value	$ (29,348)	(97)	(10,676)	(18,575)	0
Stock options exercised, shares	582
Stock options exercised, value	$ 11,208	58	11,150	0	0
Vesting of restricted stock units, shares	206
Vesting of restricted stock units, value	$ 0	21	(21)	0	0
Shares withheld for taxes, shares	(12)
Shares withheld for taxes, value	$ (383)	(1)	(382)	0	0
Net income (loss)	(31,901)	0	0	(31,901)	0
Other comprehensive loss	$ 6,027				6,027
Balances, shares at Dec. 31, 2017	49,143
Balances, value at Dec. 31, 2017	$ 1,339,138	4,914	634,192	708,181	(8,149)
Stock-based compensation expense	$ 10,089	0	10,089	0	0
Shares repurchased and retired, shares	(8,236)
Shares repurchased and retired, value	$ (211,858)	(823)	(91,520)	(119,515)	0
Stock options exercised, shares	200
Stock options exercised, value	$ 3,631	20	3,611	0	0
Vesting of restricted stock units, shares	306
Vesting of restricted stock units, value	$ 0	31	(31)	0	0
Shares withheld for taxes, shares	(56)
Shares withheld for taxes, value	$ (1,408)	(6)	(1,402)	0	0
Dividends declared	(27,209)	0	0	(27,209)	0
Net income (loss)	22,817	0	0	22,817	0
Other comprehensive loss	$ (2,975)	0	0	0	(2,975)
Balances, shares at Dec. 31, 2018	41,357
Balances, value at Dec. 31, 2018	$ 1,132,225	$ 4,136	$ 554,939	$ 584,274	$ (11,124)