Available-for-Sale Securities (Details)		3 Months Ended	9 Months Ended
	Jan. 28, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 24, 2021 USD ($)	Aug. 30, 2021 USD ($)	Jul. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale [Line Items]
Cost		$ 57,700,000	$ 57,700,000
Interest		757,000	757,000
Unrealized Gains		4,000	4,000
Unrealized Losses		(20,000)	(20,000)
Estimated Fair Value		58,441,000	58,441,000				$ 0
Principal amount		417,000	417,000				$ 565,000
Via Motor Note | Convertible Debt
Debt Securities, Available-for-sale [Line Items]
Principal amount					$ 42,500,000
Interest rate					4.00%
Silk EV Note | Convertible Debt
Debt Securities, Available-for-sale [Line Items]
Principal amount	$ 15,000,000
Interest rate	6.00%
Conversion ratio (as a percent)	0.80
Fair value adjustment of debt		4,000	(16,275)
CyVolve Note | Secured Debt
Debt Securities, Available-for-sale [Line Items]
Principal amount				$ 100,000
Interest rate				8.00%
Silk EV | Convertible promissory note and interest
Debt Securities, Available-for-sale [Line Items]
Cost		15,000,000	15,000,000
Interest		607,000	607,000
Unrealized Gains		4,000	4,000
Unrealized Losses		(20,000)	(20,000)
Estimated Fair Value	$ 15,000,000	15,591,000	15,591,000
CyVolve, Inc. | Promissory Note
Debt Securities, Available-for-sale [Line Items]
Cost		200,000	200,000
Interest		1,000	1,000
Unrealized Gains		0	0
Unrealized Losses		0	0
Estimated Fair Value		201,000	201,000	$ 100,000		$ 100,000
VIA Motors International, Inc. | Convertible promissory note and interest
Debt Securities, Available-for-sale [Line Items]
Cost		42,500,000	42,500,000
Interest		149,000	149,000
Unrealized Gains		0	0
Unrealized Losses		0	0
Estimated Fair Value		$ 42,649,000	$ 42,649,000		$ 42,500,000