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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Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

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Amount of transfers of liabilities measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Amount of transfers of financial instrument classified as a liability into level 3 of the fair value hierarchy.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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The aggregate value of all restricted investments.

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Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Fair Value, Transfers Between Level 1 and Level 2, Description and Policy [Abstract]
Transfer of fair value asset, Level 1 into Level 2	$ 0	$ 0	$ 0	$ 0
Transfer of fair value asset, Level 2 into Level 1	0	0	0	0
Transfer of fair value asset, into Level 3	0	0	0	0
Transfer of fair value asset, out of Level 3	0	0	0	0
Transfer of fair value liability, Level 1 into Level 2	0	0	0	0
Transfer of fair value liability Level 2 into Level 1	0	0	0	0
Transfer of fair value liability, into Level 3	0	0	0	0
Transfer of fair value liability, out of Level 3	0	$ 0	0	$ 0
Recurring
Assets:
Assets	320,684		320,684		$ 25,573
Recurring \| Money market funds
Assets:
Cash equivalents	177,940		177,940		24,281
Restricted cash	1,292		1,292		1,292
Recurring \| US Treasury Securities [Member]
Assets:
Marketable securities	141,452		141,452
Recurring \| Level 1
Assets:
Assets	179,232		179,232		25,573
Recurring \| Level 1 \| Money market funds
Assets:
Cash equivalents	177,940		177,940		24,281
Restricted cash	1,292		1,292		$ 1,292
Recurring \| Level 2
Assets:
Assets	141,452		141,452
Recurring \| Level 2 \| US Treasury Securities [Member]
Assets:
Marketable securities	$ 141,452		$ 141,452