Investment in Equity Securities, at fair value and long-term investments (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Change in fair value of investment in equity securities	$ (862,000)	$ 160,000	$ (1,171,000)	$ 355,000
Level 1
Equity Investments, Fair Value Disclosure	$ 1,800,000		$ 1,800,000		$ 600,000