Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Nov. 30, 2017 ft²	Dec. 31, 2018 USD ($) ft² Property	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Commitments And Contingencies [Line Items]
Additional property available under lease | Property		3
Number of built-to-suit lease properties | Property		2
Rent expenses | $		$ 2.3	$ 1.1	$ 1.0
Intellectual Property [Member]
Commitments And Contingencies [Line Items]
License obligations | $		$ 1.3
Richmond Build-to-Suit Lease [Member]
Commitments And Contingencies [Line Items]
Lease expiration date		Dec. 31, 2021
Property leased		41,400
Brisbane Build-to-Suit Lease [Member]
Commitments And Contingencies [Line Items]
Lease expiration date		May 31, 2029
Property leased	87,700	87,700
Valbonne Build-to-suit Lease [Member]
Commitments And Contingencies [Line Items]
Lease expiration date		Jun. 30, 2022
Property leased		14,036
Operating Lease One [Member] | Research and Office Space [Member]
Commitments And Contingencies [Line Items]
Area of space leased		7,700
Lease expiration date		Aug. 31, 2019
Operating Lease Two [Member]
Commitments And Contingencies [Line Items]
Area of space leased		6,200
Lease expiration date		Jul. 31, 2021