CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenue	$ 187,103	$ 117,324	$ 352,979	$ 215,920
Cost of sales	46,393	28,525	87,122	52,313
Gross profit	140,710	88,799	265,857	163,607
Selling, general, and administrative	113,355	71,689	213,787	131,814
Income from operations	27,355	17,110	52,070	31,793
Other income (expense)
Interest income, net	425	330	737	579
Other income (expense)	(2)	179	(8)	178
Other income (expense)	423	509	729	757
Income from operations before income taxes	27,778	17,619	52,799	32,550
Provision for income taxes	6,395	3,486	10,666	6,195
Net income	$ 21,383	$ 14,133	$ 42,133	$ 26,355
Basic earnings per share
Earnings per share, basic	$ 1.80	$ 1.17	$ 3.55	$ 2.19
Diluted earnings per share
Earnings per share, diluted	$ 1.75	$ 1.16	$ 3.45	$ 2.17
Weighted average shares outstanding -
Basic	11,861	12,037	11,870	12,032
Diluted	12,218	12,174	12,229	12,129
Cash dividends declared per share	$ 0.75	$ 0.48	$ 1.50	$ 0.96