Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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Available-for-Sale Security (Details)		3 Months Ended		6 Months Ended
Available-for-Sale Security (Details)	Jan. 28, 2021 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale [Line Items]
Payments to acquire debt securities				$ 15,528,000	$ 0
Principal Amount		$ 81,224,000		81,224,000		$ 565,000
Changes in fair value of available-for-sale securities		$ (20,000)	$ 0	$ (20,000)	$ 0
Convertible Promissory Note \| Silk EV
Debt Securities, Available-for-sale [Line Items]
Payments to acquire debt securities	$ 15,000,000.0
Principal Amount	$ 15,000,000.0
Interest rate	6.00%
Conversion ratio (as a percent)	0.80