Organization - Additional Information (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2021 USD ($) Subsidiary	Dec. 31, 2020 USD ($)
Accounting Policies [Abstract]
Number of subsidiaries \| Subsidiary	3
Accumulated deficit	$ 643,327	$ 621,205
Cash, cash equivalents and marketable securities	$ 121,414	$ 61,761

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 65
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant