COMMITMENTS AND CONTINGENCIES - Additional Information (Detail) $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended
	Apr. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ft²	Jun. 30, 2020 USD ($) ft²	May 31, 2020 USD ($) ft²
Commitments And Contingencies [Line Items]
Operating lease costs		$ 2,600	$ 5,100
Variable lease expense		$ 500	1,000
Cash paid for operating lease liabilities included net cash used in operating activities			$ 3,100
Operating lease, weighted-average remaining lease term		8 years 3 months 18 days	8 years 3 months 18 days
Operating lease, weighted-average discount rate		6.20%	6.20%
Total lease payment		$ 42,610	$ 42,610
License obligations		1,200	1,200
Manufacturing Capacity [Member]
Commitments And Contingencies [Line Items]
Other commitment		3,200	3,200
Payments for other commitment	$ 3,000
Manufacturing Obligations [Member]
Commitments And Contingencies [Line Items]
Other commitment		2,000	2,000
Payments for other commitment	1,000
Non-cancelable Contractual Commitment [Member]
Commitments And Contingencies [Line Items]
Contractual obligation		$ 2,500	$ 2,500
Contractual obligation paid upon execution	$ 500
Minimum
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term		5 years	5 years
Maximum
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term		10 years	10 years
Richmond, California
Commitments And Contingencies [Line Items]
Lease not yet commenced, amount				$ 1,600
Lease not yet commenced, area of real estate | ft²				8,500
Office and Laboratory | Brisbane, California
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) | ft²		87,700	87,700
Operating Lease One | Office and Laboratory | Richmond, California
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) | ft²		45,600	45,600
Operating Lease One | Research and Office Space | Valbonne, France
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) | ft²		20,800	20,800