Accrued expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued expenses
Accrued savings offers	$ 16,790	$ 11,289
Accrued rebates	6,109	7,762
Accrued customer returns	5,122	5,157
Accrued wholesaler fees	5,014	4,249
Accrued payroll and benefits	4,485	4,555
Other accrued expenses	2,668	2,806
Total accrued expenses	$ 40,188	$ 35,818