Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Consolidated Statements of Income (Unaudited) [Abstract]
Revenue	$ 677,026	$ 518,028
Cost of sales	170,566	125,793
Gross profit	506,460	392,235
Operating expenses:
Selling expenses	273,746	206,042
General and administrative expenses	169,801	149,628
Total operating expenses	443,547	355,670
Operating income	62,913	36,565
Other income (expense), net	1,582	(6,174)
Income before provision for income taxes	64,495	30,391
Provision for income taxes	17,065	10,661
Net income	$ 47,430	$ 19,730
Net income per share (Note 6):
Basic (in dollars per share)	$ 0.94	$ 0.36
Diluted (in dollars per share)	$ 0.91	$ 0.36
Weighted-average common shares outstanding:
Basic (in shares)	50,706	55,059
Diluted (in shares)	52,172	55,101