Consolidated statements of operations and comprehensive income - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Mar. 31, 2020	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales	$ 74,712	$ 80,760	$ 67,615	$ 59,764	$ 66,141	$ 78,571	$ 63,889	$ 59,055	$ 65,920	$ 282,851	$ 267,435	$ 269,888
Cost of sales					25,650				25,712	101,728	104,694	105,163
Gross profit	48,064	52,520	43,348	37,191	40,491	46,919	38,969	36,645	40,208	181,123	162,741	164,725
Selling, general, and administrative expenses					37,324				36,234	157,155	136,579	131,446
Restructuring (income) expense					22,176				0	(5,982)	0	0
Operating income (loss)					(19,009)				3,974	29,950	26,162	33,279
Other income (expense), net					(315)				(888)	426	(390)	(2,035)
Interest expense, net					(1,849)				(1,963)	(6,307)	(7,816)	(8,775)
Income (loss) before provision for income taxes					(21,173)				1,123	24,069	17,956	22,469
Income tax (provision) benefit					3,259				(433)	(6,185)	(2,431)	11,006
Net income (loss)	$ (341)	$ 8,002	$ 6,517	$ 3,706	(17,914)	$ 9,672	$ 3,915	$ 1,248	690	17,884	15,525	33,475
Comprehensive income (loss)					$ (17,914)				$ 690	$ 17,884	$ 15,525	$ 33,475
Net income (loss) per share:
Basic (in USD per share)	$ (0.01)	$ 0.16	$ 0.13	$ 0.08	$ (0.37)	$ 0.20	$ 0.08	$ 0.03	$ 0.01	$ 0.37	$ 0.33	$ 0.74
Diluted (in USD per share)	$ (0.01)	$ 0.16	$ 0.13	$ 0.07	$ (0.37)	$ 0.20	$ 0.08	$ 0.03	$ 0.01	$ 0.35	$ 0.32	$ 0.68
Weighted average shares outstanding:
Basic (in shares)					48,022,926				46,435,560	48,498,813	46,828,798	45,358,452
Diluted (in shares)					48,022,926				49,302,771	50,817,143	49,268,616	49,374,758