Investments (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Sep. 08, 2017
Schedule of Equity Method Investments
(Loss) income from equity method investments	$ (7,400,000)	$ 1,300,000	$ (11,562,000)	$ 6,000,000
Distributions received		0		0	$ 8,600,000
Equity method investment	88,315,000		88,315,000		99,966,000
Unrealized (gains) loss on marketable securities	0	$ 17,100,000	(26,800,000)	$ 21,000,000.0
Other Assets
Schedule of Equity Method Investments
Equity method investment	88,300,000		88,300,000		100,000,000.0
Alternative investment	$ 67,300,000		$ 67,300,000		$ 94,100,000
CF Real Estate Finance Holdings, L.P.
Schedule of Equity Method Investments
Equity method investment ownership percentage (in percentage)	27.00%		27.00%
Equity method investment						$ 100,000,000.0