Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Consolidated Statements of Income (Unaudited) [Abstract]
Revenue	$ 428,416	$ 383,553	$ 1,248,687	$ 1,136,039
Cost of sales	70,631	68,755	242,453	201,525
Gross profit	357,785	314,798	1,006,234	934,514
Operating expenses:
Selling expenses	184,203	162,402	536,845	477,403
General and administrative expenses	106,369	99,501	311,223	298,938
Total operating expenses	290,572	261,903	848,068	776,341
Operating income	67,213	52,895	158,166	158,173
Other income (expense), net	(6,879)	(674)	(7,428)	(7,347)
Income before provision for income taxes	60,334	52,221	150,738	150,826
Provision for income taxes	13,536	16,932	46,931	52,105
Net income	$ 46,798	$ 35,289	$ 103,807	$ 98,721
Net income per share (Note 2):
Basic (in dollars per share)	$ 0.75	$ 0.57	$ 1.67	$ 1.58
Diluted (in dollars per share)	$ 0.72	$ 0.55	$ 1.61	$ 1.53
Weighted-average common shares outstanding (000s):
Basic (in shares)	62,285	61,971	61,998	62,443
Diluted (in shares)	64,708	64,065	64,408	64,584