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

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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.

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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. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
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-Publisher FASB
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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.

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-Topic 820
-SubTopic 10
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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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Fair value of financial instruments - Schedule of cash equivalents and investments carried at fair value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Jan. 01, 2018
Fair Value, Measurements, Recurring
Assets:
Total assets	$ 25,985	$ 39,971
Liabilities:
Total liabilities	1,705	2,486
Fair Value, Measurements, Recurring \| (Level 1)
Assets:
Total assets	25,985	39,971
Liabilities:
Warrant liability	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring \| (Level 2)
Assets:
Total assets	0	0
Liabilities:
Warrant liability	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring \| (Level 3)
Assets:
Total assets	0	0
Liabilities:
Warrant liability	1,705	2,486
Total liabilities	1,705	2,486
Money market funds \| Fair Value, Measurements, Recurring
Assets:
Included in cash equivalents	25,985	39,971
Money market funds \| Fair Value, Measurements, Recurring \| (Level 1)
Assets:
Included in cash equivalents	25,985	39,971
Money market funds \| Fair Value, Measurements, Recurring \| (Level 2)
Assets:
Included in cash equivalents	0	0
Money market funds \| Fair Value, Measurements, Recurring \| (Level 3)
Assets:
Included in cash equivalents	0	0
Warrants \| (Level 3)
Liabilities:
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	$ 1,705	$ 2,486	$ 18,200