Accrued expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accrued expenses
Accrued savings offers	$ 16,529	$ 11,289
Accrued rebates	5,065	7,762
Accrued customer returns	5,286	5,157
Accrued wholesaler fees	4,030	4,249
Accrued payroll and benefits	4,069	4,555
Other accrued expenses	2,869	2,806
Total accrued expenses	$ 37,848	$ 35,818