Financial Instruments - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Cost method investments	$ 2,000,000	$ 2,000,000
Non-cash impairment charge	499,000	1,919,000
Available-for-sale debt securities in unrealized loss position	0	0	$ 46,550,000
Unrealized losses	0	0	22,000
Accrued interest	103,000	103,000	183,000
Available-for-sale, credit loss	$ 0	$ 0	$ 0