Customer, Supplier and Product Concentration - Disaggregation of Revenue by Customer (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Concentration Risk [Line Items]
Revenues, net	$ 165,871	$ 184,063
Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	100.00%	100.00%
Big 3 Wholesalers combined
Concentration Risk [Line Items]
Revenues, net	$ 97,609	$ 118,365
Big 3 Wholesalers combined | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	58.80%	64.30%
Amerisource
Concentration Risk [Line Items]
Revenues, net	$ 30,096	$ 37,955
Amerisource | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	18.10%	20.60%
Cardinal
Concentration Risk [Line Items]
Revenues, net	$ 29,761	$ 27,189
Cardinal | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	17.90%	14.80%
McKesson
Concentration Risk [Line Items]
Revenues, net	$ 37,752	$ 53,221
McKesson | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	22.80%	28.90%
All Others
Concentration Risk [Line Items]
Revenues, net	$ 68,262	$ 65,698
All Others | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	41.20%	35.70%