Fair Value Measurements (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Gains and losses on equity instruments
Net (losses) gains recognized during the period on equity investments	$ (176,000)	$ 87,000
Less: net gains recognized during the period on equity investments sold during the period	25,000
Unrealized (losses) gains recognized during the period on equity investments still held at period end	(201,000)	$ 87,000
Total
Fair Value Measurements
Equity investments	1,010,000		$ 1,182,000
Level 1
Fair Value Measurements
Equity investments	$ 1,010,000		$ 1,182,000