Summary of Significant Accounting Policies - Concentrations (Details) - item	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Total net revenue
Concentrations
Concentration risk (as a percentage)	88.00%	32.00%	81.00%	13.00%
Total net revenue | Customer 1
Concentrations
Concentration risk (as a percentage)	34.00%	11.00%	28.00%	4.00%
Total net revenue | Customer 2
Concentrations
Concentration risk (as a percentage)	28.00%	9.00%	28.00%	3.00%
Total net revenue | Customer 3
Concentrations
Concentration risk (as a percentage)	25.00%	12.00%	25.00%	5.00%
Total net revenue | Customer risk | Three major pharmaceutical distributors
Concentrations
Number of major distributors			3
Total net revenue | Customer risk | Three major pharmaceutical distributors | Minimum
Concentrations
Concentration risk (as a percentage)			10.00%
Total accounts receivable | Customer 1
Concentrations
Concentration risk (as a percentage)			35.00%		30.00%
Total accounts receivable | Customer 2
Concentrations
Concentration risk (as a percentage)			29.00%		31.00%
Total accounts receivable | Customer 3
Concentrations
Concentration risk (as a percentage)			26.00%		35.00%