Consolidated Statement of Stockholders' Equity (Unaudited) (USD $) In Thousands	Total	Common Stock	Additional Paid-in-Capital	Retained Earnings	Unrealized Gains (Losses) on Interest Rate Swaps	Unrealized Gains (Losses) on Marketable Securities	Unrealized Gains (Losses) on Currency Translation	Treasury Stock
Beginning balance at Dec. 31, 2010	$ 784,368	$ 261	$ 363,966	$ 519,843	$ (10,953)	$ 50	$ (7,852)	$ (80,947)
Beginning balance, shares at Dec. 31, 2010		26,096
Comprehensive income:
Net income	61,539			61,539
Interest rate swap adjustment, net of tax provision of $5,717	(9,528)				(9,528)
Unrealized loss on investments, net of tax benefit of $13	(22)					(22)
Unrealized gain on currency translation	319						319
Total comprehensive income	52,308
Purchases of treasury stock	(50,778)							(50,778)
Issuance of common and treasury shares to employee benefit plans	(1,102)	(2)	(7,417)					6,317
Issuance of common and treasury shares to employee benefit plans, shares		(188)
Proceeds from sales of common stock under employee benefit plans	3,094	1	3,093
Proceeds from sales of common stock under employee benefit plans, shares		81
Issuance of restricted stock		3	(3)
Issuance of restricted stock, shares		300
Forfeiture of restricted stock		(1)	1
Forfeiture of restricted stock, shares		(85)
Stock-based compensation	8,333		8,333
Tax effect from options exercised and the vesting of restricted shares	803		803
Cash dividends	(8,262)			(8,262)
Ending balance at Sep. 30, 2011	$ 788,764	$ 262	$ 368,776	$ 573,120	$ (20,481)	$ 28	$ (7,533)	$ (125,408)
Ending balance, shares at Sep. 30, 2011		26,204