Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Current income taxes
Federal	$ 63,758	$ 71,032	$ 48,523
State	12,226	16,764	10,350
Foreign	7,487	3,648	2,123
Total	83,471	91,444	60,996
Deferred income taxes
Federal	1,003	(2,182)	4,752
State	(1,067)	377	587
Foreign	(3)	93	(31)
Total	(67)	(1,712)	5,308
Income taxes
Federal	64,761	68,850	53,275
State	11,159	17,141	10,937
Foreign	7,484	3,741	2,092
Total income taxes	83,404	89,732	66,304
Foreign income before income taxes	108,738	43,327	27,912
Actual income taxes differed from that obtained by applying the statutory federal income tax rate to income before income taxes
Computed "expected" income taxes	99,842	87,517	64,105
State income taxes, net of federal income tax benefit	6,912	10,566	7,600
Foreign rate differential	(24,783)	(11,304)	(7,878)
Other	1,433	2,953	2,477
Total income taxes	83,404	89,732	66,304
Deferred tax assets (liabilities), current:
Uniform capitalization adjustment to inventory	5,271	3,127
Bad debt and other reserves	8,874	7,365
State taxes	1,729	4,360
Prepaid expenses	(1,460)	(2,850)
Total deferred tax assets, current	14,414	12,002
Deferred tax assets (liabilities), noncurrent:
Amortization and impairment of intangible assets	7,181	6,262
Depreciation of property and equipment	(6,056)	(3,230)
Share-based compensation	11,305	11,105
Foreign currency translation	(744)	(1,062)
Deferred rent	169	1,245
Acquisition cost	808
Other	63	63
Net operating loss carryforwards	497	738
Total deferred tax assets, noncurrent	13,223	15,121
Net deferred tax assets	$ 27,637	$ 27,123