Schedule II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for chargebacks
Movement in valuation and qualifying accounts
Balance at beginning of period	$ 816	$ 779	$ 940
Additions charged to costs and expenses	8,565	10,146	10,504
Deductions and Payments	(8,067)	(10,109)	(10,665)
Balance at end of period	1,314	816	779
Allowance for cash discounts
Movement in valuation and qualifying accounts
Balance at beginning of period	337	171	99
Additions charged to costs and expenses	3,519	1,814	772
Deductions and Payments	(3,305)	(1,648)	(700)
Balance at end of period	551	337	171
Sales offers
Movement in valuation and qualifying accounts
Balance at beginning of period	7,168	2,070
Additions charged to costs and expenses	71,303	30,978	5,816
Deductions and Payments	(67,183)	(25,880)	(3,746)
Balance at end of period	11,288	7,168	2,070
Reserve for wholesaler fees
Movement in valuation and qualifying accounts
Balance at beginning of period	2,345	509	361
Additions charged to costs and expenses	17,414	8,244	2,838
Deductions and Payments	(15,510)	(6,408)	(2,690)
Balance at end of period	4,249	2,345	509
Reserve for returns
Movement in valuation and qualifying accounts
Balance at beginning of period	2,711	1,157	429
Additions charged to costs and expenses	3,803	1,792	764
Deductions and Payments	(1,357)	(238)	(36)
Balance at end of period	5,157	2,711	1,157
Rebates
Movement in valuation and qualifying accounts
Balance at beginning of period	4,008	544	110
Additions charged to costs and expenses	18,746	7,837	519
Deductions and Payments	(14,991)	(4,373)	(85)
Balance at end of period	$ 7,763	$ 4,008	$ 544