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, 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 income (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)
Balances, shares at Mar. 31, 2018	47,572	47,572
Balances, value at Mar. 31, 2018	$ 1,247,331	$ 4,757	608,092	640,466	(5,984)
Stock-based compensation expense	$ 2,535	$ 0	2,535	0	0
Shares repurchased and retired, shares	(263)	(263)
Shares repurchased and retired, value	$ (7,487)	$ (26)	(2,931)	(4,530)	0
Stock options exercised, shares	14	14
Stock options exercised, value	$ 298	$ 1	297	0	0
Vesting of restricted stock units, shares	11	11
Vesting of restricted stock units, value	$ 0	$ 1	(1)	0	0
Shares withheld for taxes, shares	0	0
Shares withheld for taxes, value	$ (8)	$ 0	(8)	0	0
Dividends declared	(7,100)	0	0	(7,100)	0
Net income (loss)	10,943	0	0	10,943	0
Other comprehensive loss	$ (2,367)	$ 0	0	0	(2,367)
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)
Balances, shares at Dec. 31, 2018	41,357	41,357
Balances, value at Dec. 31, 2018	$ 1,132,225	$ 4,136	554,939	584,274	(11,124)
Stock-based compensation expense	$ 5,720	$ 0	5,720	0	0
Shares repurchased and retired, shares	(3,908)	(3,908)
Shares repurchased and retired, value	$ (100,039)	$ (391)	(43,424)	(56,224)	0
Stock options exercised, shares	33	33
Stock options exercised, value	$ 693	$ 3	690	0	0
Vesting of restricted stock units, shares	242	242
Vesting of restricted stock units, value	$ 0	$ 24	(24)	0	0
Shares withheld for taxes, shares	(45)	(45)
Shares withheld for taxes, value	$ (1,242)	$ (4)	(1,238)	0	0
Dividends declared	(11,527)	0	0	(11,527)	0
Net income (loss)	23,220	0	0	23,220	0
Other comprehensive loss	$ (4,000)	$ 0	0	0	(4,000)
Balances, shares at Jun. 30, 2019	37,679	37,679
Balances, value at Jun. 30, 2019	$ 1,045,050	$ 3,768	516,663	539,743	(15,124)
Balances, shares at Mar. 31, 2019	39,169	39,169
Balances, value at Mar. 31, 2019	$ 1,078,725	$ 3,917	530,261	557,804	(13,257)
Stock-based compensation expense	$ 2,948	$ 0	2,948	0	0
Shares repurchased and retired, shares	(1,525)	(1,525)
Shares repurchased and retired, value	$ (38,959)	$ (152)	(16,951)	(21,856)	0
Stock options exercised, shares	20	20
Stock options exercised, value	$ 414	$ 2	412	0	0
Vesting of restricted stock units, shares	15	15
Vesting of restricted stock units, value	$ 0	$ 1	(1)	0	0
Shares withheld for taxes, shares	0	0
Shares withheld for taxes, value	$ (6)	$ 0	(6)	0	0
Dividends declared	(5,652)	0	0	(5,652)	0
Net income (loss)	9,447	0	0	9,447	0
Other comprehensive loss	$ (1,867)	$ 0	0	0	(1,867)
Balances, shares at Jun. 30, 2019	37,679	37,679
Balances, value at Jun. 30, 2019	$ 1,045,050	$ 3,768	$ 516,663	$ 539,743	$ (15,124)