Cash and cash equivalents restricted cash maximum investments maturity period.

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Impairment of right-of-use assets.

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Right-of-use and leasehold improvement assets measurement input.

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Significant accounting policies.

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Working capital.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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Amount before accumulated depreciation of additions or improvements to assets held under a lease arrangement.

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Indicates (true false) whether lessee has option to extend operating lease.

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The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) Segment	Dec. 31, 2019 USD ($)
Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 53,967,000		$ 53,967,000	$ 65,134,000
Accumulated deficit	(496,608,000)		(496,608,000)	(470,111,000)
Working capital	50,600,000		$ 50,600,000
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	2,914,000		$ 5,784,000	$ 0
Impairments of right-of-use assets	2,400,000	$ 2,400,000
leasehold improvement assets	$ 500,000	$ 500,000	$ 500,000
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