Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended			9 Months Ended
	Mar. 31, 2021 USD ($) Segment	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 78,682,000				$ 60,541,000
Accumulated deficit	(508,658,000)				$ (500,654,000)
Working capital	$ 72,400,000
Number of operating segment | Segment	1
Cash and cash equivalents, restricted cash maturity period	Three months or less
Lessee, operating lease, existence of option to extend	true		true
Lessee, operating lease, existence of option to terminate	true		true
Impairments of long-lived assets	$ 0		$ 2,870,000	$ 5,800,000
Impairments of right-of-use assets		$ 2,400,000	2,400,000
leasehold improvement assets		$ 500,000	$ 500,000	$ 500,000
ASU No. 2019-12 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Early Adoption [true false]	true
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2021
Assembled Workforce [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	3 years
Discounted Cash Flows [Member]
Significant Accounting Policies [Line Items]
Right-of-use and leasehold improvement assets, discount rate		0.095	0.095	0.095
Minimum [Member]
Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	5 years