Consolidated Statements Of Shareholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balances, value at Dec. 31, 2014	$ 1,291,040	$ 5,300	$ 649,715	$ 645,500	$ (9,475)
Balances, shares at Dec. 31, 2014	52,994	52,994
Stock-based compensation expense	1,940	0	1,940	0	0
Shares repurchased and retired, shares		(663)
Shares repurchased and retired, value	(15,778)	(67)	(7,230)	(8,481)	0
Stock options exercised, shares	46	46
Stock options exercised, value	821	5	816	0	0
Vesting of restricted stock units, shares		120
Vesting of restricted stock units, value	0	12	(12)	0	0
Shares withheld for taxes, shares		(19)
Shares withheld for taxes, value	(457)	(2)	(455)	0	0
Excess tax benefit of stock-based compensation	292	0	292	0	0
Comprehensive income	10,744	0	0	14,205	(3,461)
Balances, value at Mar. 31, 2015	$ 1,288,602	$ 5,248	$ 645,066	$ 651,224	$ (12,936)
Balances, shares at Mar. 31, 2015	52,478	52,478