Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018 USD ($) Customer	Jan. 01, 2019 USD ($)	Dec. 31, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Carrying value of finished goods inventory	$ 2,844,000		$ 67,000
Accrued liability related to excess inventory purchase commitments	2,800,000
Impairment losses	0
Interest or penalties charged to the underpayment of income taxes	$ 0
Accounting Standards Update (“ASU”) No. 2016-02 | Subsequent Event
Summary Of Significant Accounting Policies [Line Items]
Operating leases, right-of-use assets		$ 2,100,000
Operating leases, liabilities		$ 3,300,000
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful lives	5 years
Leasing arrangements terms	1 year
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful lives	2 years
Andexxa Specialty Distributor | Customer Concentration Risk | Sales Revenue, Net
Summary Of Significant Accounting Policies [Line Items]
Number of customer | Customer	3
Andexxa Specialty Distributor | Customer Concentration Risk | Sales Revenue, Net | Minimum
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	10.00%