Customer, Supplier and Product Concentration - Percentage of the Company's Gross and Net Sales and Accounts Receivable (Details) - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gross Sales
Concentration Risk [Line Items]
Customer concentration	80.20%	77.40%	77.80%
Net Revenue
Concentration Risk [Line Items]
Customer concentration	63.50%	63.80%	70.00%
Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration	86.00%	83.90%	82.80%
Amerisource | Gross Sales
Concentration Risk [Line Items]
Customer concentration	23.60%	29.50%	28.00%
Amerisource | Net Revenue
Concentration Risk [Line Items]
Customer concentration	19.10%	23.30%	23.20%
Amerisource | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration	26.30%	35.60%	28.80%
Cardinal | Gross Sales
Concentration Risk [Line Items]
Customer concentration	17.50%	15.40%	19.70%
Cardinal | Net Revenue
Concentration Risk [Line Items]
Customer concentration	17.90%	16.30%	19.50%
Cardinal | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration	21.10%	15.10%	26.10%
McKesson | Gross Sales
Concentration Risk [Line Items]
Customer concentration	39.10%	32.50%	30.10%
McKesson | Net Revenue
Concentration Risk [Line Items]
Customer concentration	26.50%	24.20%	27.30%
McKesson | Gross Accounts Receivable
Concentration Risk [Line Items]
Customer concentration	38.60%	33.20%	27.90%