Fair Value Measurements - Summary of Financial Assets and Liabilities are Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Liabilities
Derivative liability related to loan		$ 494	$ 390
Fair Value Measurements Recurring
Assets
Restricted cash	$ 263	263	262
Total assets	62,367	23,047	55,553
Liabilities
Derivative liability related to loan		494	390
Total liabilities		494	390
Fair Value Measurements Recurring \| Money Market Funds
Assets
Cash equivalents - money market funds	62,104	22,784	55,291
Fair Value Measurements Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Total assets	62,104	22,784	55,291
Fair Value Measurements Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money Market Funds
Assets
Cash equivalents - money market funds	62,104	22,784	55,291
Fair Value Measurements Recurring \| Significant Other Observable Inputs (Level 2)
Assets
Restricted cash	263	263	262
Total assets	$ 263	263	262
Fair Value Measurements Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities
Derivative liability related to loan		494	390
Total liabilities		$ 494	$ 390

Restricted Cash Fair Value Disclosure

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ 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 (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Fair value portion 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.

+ References

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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- Definition

Fair value of financial and nonfinancial obligations.

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