Commitments and Contingencies - Operating Leases - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2016 ft²	Dec. 31, 2016 USD ($) ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Commitments And Contingencies [Line Items]
Rent expense, net of sublease income | $		$ 2.0	$ 0.4	$ 0.3
Operating Lease Two [Member] | Multi Tenant Building [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease | ft²	19,805	22,067
Lease expire date	Feb. 28, 2022	Feb. 28, 2022
Commencement date of lease	Sep. 30, 2016