Stockholders' Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 81,752	$ 85,114	$ 80,747	$ 11,391	$ 80,747	$ 20,952
Other comprehensive income (loss) before reclassifications	(138)	352	10
Net losses (gains) reclassified from accumulated other comprehensive loss		3
Net current period other comprehensive income	(138)	355	10	0	227	0
Ending balance	73,428	81,752	85,114	64,952	73,428	64,952
Gross realized gains, available for sale securities	23
Gross realized losses, available for sale securities	6
Proceeds from sale of debt securities, available-for-sale	9,404
Unrealized gains (losses) on short-term investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	338	(17)	(27)		(27)
Other comprehensive income (loss) before reclassifications	(138)	352	10
Net losses (gains) reclassified from accumulated other comprehensive loss		3
Net current period other comprehensive income	(138)	355	10
Ending balance	200	338	(17)		200
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	338	(17)	(27)	0	(27)	0
Net current period other comprehensive income	(138)	355	10
Ending balance	$ 200	$ 338	$ (17)	$ 0	$ 200	$ 0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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