Customer, Supplier and Product Concentration - Disaggregation of Revenue by Customer (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Concentration Risk [Line Items]
Revenues, net	$ 184,063	$ 253,420
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	$ 118,365	$ 162,616
Big 3 Wholesalers combined | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	64.30%	64.20%
Amerisource
Concentration Risk [Line Items]
Revenues, net	$ 37,955	$ 43,937
Amerisource | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	20.60%	17.30%
Cardinal
Concentration Risk [Line Items]
Revenues, net	$ 27,189	$ 48,968
Cardinal | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	14.80%	19.30%
McKesson
Concentration Risk [Line Items]
Revenues, net	$ 53,221	$ 69,711
McKesson | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	28.90%	27.50%
All Others
Concentration Risk [Line Items]
Revenues, net	$ 65,698	$ 90,804
All Others | Net Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk percentage	35.70%	35.80%