Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current income taxes
Federal	$ 50,911	$ 63,758	$ 71,032
State	6,482	12,226	16,764
Foreign	3,368	7,487	3,648
Total	60,761	83,471	91,444
Deferred income taxes
Federal	(6,083)	1,003	(2,182)
State	414	(1,067)	377
Foreign	12	(3)	93
Total	(5,657)	(67)	(1,712)
Income taxes
Federal	44,828	64,761	68,850
State	6,896	11,159	17,141
Foreign	3,380	7,484	3,741
Total income taxes	55,104	83,404	89,732
Foreign income before income taxes	51,409	108,738	43,327
Actual income taxes differed from that obtained by applying the statutory federal income tax rate to income before income taxes
Computed "expected" income taxes	64,282	99,842	87,517
State income taxes, net of federal income tax benefit	3,562	6,912	10,566
Foreign rate differential	(12,908)	(24,783)	(11,304)
Other	168	1,433	2,953
Total income taxes	55,104	83,404	89,732
Deferred tax assets (liabilities), current:
Uniform capitalization adjustment to inventory	6,870	5,271
Bad debt and other reserves	11,582	8,874
State taxes	799	1,729
Prepaid expenses	(1,961)	(1,460)
Total deferred tax assets, current	17,290	14,414
Deferred tax assets (liabilities), noncurrent:
Amortization and impairment of intangible assets	5,312	7,181
Depreciation of property and equipment	(8,524)	(6,056)
Share-based compensation	11,906	11,305
Foreign currency translation	244	(744)
Deferred rent	3,247	169
Acquisition cost	834	808
Other	111	63
Net operating loss carryforwards	242	497
Total deferred tax assets, noncurrent	13,372	13,223
Net deferred tax assets	$ 30,662	$ 27,637