Fair Value of Financial Instruments - Summary of Changes in Fair Value of Level 3 Financial Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, beginning of period	$ 5,373	$ 11,844
Change in fair value of Level 3 financial liabilities	(2,869)	3,120
Fair value, end of period	2,504	14,872
2016 Placement Warrants
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value of Placement Warrants at exercise	0	(66)
2017 Placement Warrants
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value of Placement Warrants at exercise	$ 0	$ (26)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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