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	$ 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 income (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)
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)
Stock-based compensation expense	$ 2,824	$ 0	2,824	0	0
Shares repurchased and retired, shares	(2,227)	(2,227)
Shares repurchased and retired, value	$ (46,185)	$ (223)	(14,730)	(31,232)	0
Stock options exercised, shares	5	5
Stock options exercised, value	$ 86	$ 1	85	0	0
Vesting of restricted stock units, shares	20	20
Vesting of restricted stock units, value	$ 0	$ 2	(2)	0	0
Shares withheld for taxes, shares	(2)	(2)
Shares withheld for taxes, value	$ (51)	$ 0	(51)	0	0
Dividends declared	(6,769)	0	0	(6,769)	0
Net income (loss)	7,799	0	0	7,799	0
Other comprehensive loss	$ (167)	$ 0	0	0	(167)
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)
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	$ 8,461	$ 0	8,461	0	0
Shares repurchased and retired, shares	(4,590)	(4,590)
Shares repurchased and retired, value	$ (118,350)	$ (459)	(51,004)	(66,887)	0
Stock options exercised, shares	65	65
Stock options exercised, value	$ 1,350	$ 6	1,344	0	0
Vesting of restricted stock units, shares	252	252
Vesting of restricted stock units, value	$ 0	$ 25	(25)	0	0
Shares withheld for taxes, shares	(48)	(48)
Shares withheld for taxes, value	$ (1,318)	$ (4)	(1,314)	0	0
Dividends declared	(17,083)	0	0	(17,083)	0
Net income (loss)	30,356	0	0	30,356	0
Other comprehensive loss	$ (6,869)	$ 0	0	0	(6,869)
Balances, shares at Sep. 30, 2019	37,036	37,036
Balances, value at Sep. 30, 2019	$ 1,028,772	$ 3,704	512,401	530,660	(17,993)
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)
Stock-based compensation expense	$ 2,741	$ 0	2,741	0	0
Shares repurchased and retired, shares	(682)	(682)
Shares repurchased and retired, value	$ (18,311)	$ (68)	(7,580)	(10,663)	0
Stock options exercised, shares	32	32
Stock options exercised, value	$ 657	$ 3	654	0	0
Vesting of restricted stock units, shares	10	10
Vesting of restricted stock units, value	$ 0	$ 1	(1)	0	0
Shares withheld for taxes, shares	(3)	(3)
Shares withheld for taxes, value	$ (76)	$ 0	(76)	0	0
Dividends declared	(5,556)	0	0	(5,556)	0
Net income (loss)	7,136	0	0	7,136	0
Other comprehensive loss	$ (2,869)	$ 0	0	0	(2,869)
Balances, shares at Sep. 30, 2019	37,036	37,036
Balances, value at Sep. 30, 2019	$ 1,028,772	$ 3,704	$ 512,401	$ 530,660	$ (17,993)