Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Consolidated Statements of Income (Unaudited) [Abstract]
Revenue	$ 604,162	$ 571,308	$ 1,676,468	$ 1,674,849
Cost of sales	125,863	152,755	391,937	368,073
Gross profit	478,299	418,553	1,284,531	1,306,776
Operating expenses:
Selling expenses	255,274	240,260	699,196	713,714
General and administrative expenses	140,651	135,752	415,014	410,074
Total operating expenses	395,925	376,012	1,114,210	1,123,788
Operating income	82,374	42,541	170,321	182,988
Other income (expense), net	(5,695)	(14,428)	(19,618)	(29,454)
Income before provision for income taxes	76,679	28,113	150,703	153,534
Provision for income taxes	19,807	11,846	45,802	56,328
Net income	$ 56,872	$ 16,267	$ 104,901	$ 97,206
Net income per share (Note 2):
Basic (in dollars per share)	$ 1.02	$ 0.28	$ 1.87	$ 1.66
Diluted (in dollars per share)	$ 0.98	$ 0.28	$ 1.85	$ 1.63
Weighted-average common shares outstanding:
Basic (in shares)	55,983	57,725	55,963	58,403
Diluted (in shares)	57,852	58,663	56,586	59,565