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