Consolidated Statements Of Shareholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]
Balances, value at Dec. 31, 2013	$ 1,227,033	$ 5,383	$ 644,594	$ 586,422	$ (9,094)	$ (272)
Balances, shares at Dec. 31, 2013	53,825	53,825
Stock-based compensation expense	6,163		6,163
Shares repurchased and retired, shares		(1,054)
Shares repurchased and retired, value	(25,045)	(105)	(11,440)	(13,500)
Stock options exercised, shares	612	612
Stock options exercised, value	11,748	60	11,688
Issuance of restricted shares, net of forfeitures, shares		95
Issuance of restricted shares, net of forfeitures, value	0	10	(10)
Restricted shares withheld for taxes, shares		(13)
Restricted shares withheld for taxes	(309)	(1)	(308)
Excess tax benefit of stock-based compensation	59		59
Cancellation of treasury shares	0		(272)			272
Comprehensive income	56,805			58,431	(1,626)
Balances, value at Sep. 30, 2014	$ 1,276,454	$ 5,347	$ 650,474	$ 631,353	$ (10,720)	$ 0
Balances, shares at Sep. 30, 2014	53,465	53,465