Customer, Supplier and Product Concentration - Disaggregation of Revenue by Customer (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Concentration Risk [Line Items]
Revenues, net	$ 176,244	$ 165,625	$ 520,172	$ 540,632
Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
Big 3 Wholesalers combined
Concentration Risk [Line Items]
Revenues, net	$ 106,512	$ 103,722	$ 313,478	$ 334,333
Big 3 Wholesalers combined | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	60.40%	62.60%	60.30%	61.80%
Amerisource
Concentration Risk [Line Items]
Revenues, net	$ 36,831	$ 36,613	$ 107,203	$ 113,824
Amerisource | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	20.90%	22.10%	20.60%	21.10%
Cardinal
Concentration Risk [Line Items]
Revenues, net	$ 31,156	$ 26,835	$ 89,255	$ 83,886
Cardinal | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	17.70%	16.20%	17.20%	15.50%
McKesson
Concentration Risk [Line Items]
Revenues, net	$ 38,525	$ 40,274	$ 117,020	$ 136,623
McKesson | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	21.90%	24.30%	22.50%	25.30%
All Others
Concentration Risk [Line Items]
Revenues, net	$ 69,732	$ 61,903	$ 206,694	$ 206,299
All Others | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	39.60%	37.40%	39.70%	38.20%