Other Assets (Capital Contributions Made to Loan Origination Partners) (Details) - USD ($)		3 Months Ended			9 Months Ended
	Jul. 01, 2021	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Other Assets [Line Items]
Gain on investment in Lima One common equity (Note 16)		$ 38,933,000	$ 0		$ 38,933,000	$ 0
Impairment (reversal) on investment		(10,000,000)
Lima One
Other Assets [Line Items]
Gain on investment in Lima One common equity (Note 16)	$ 38,900,000
Impairment (reversal) on investment	$ (5,000,000)			$ 21,000,000
Loan Originators
Other Assets [Line Items]
Equity method investments		23,200,000			23,200,000
Impairment (reversal) on investment		0			0	$ 65,200,000
Company’s residential whole loans at carrying value are serviced by entities the Company has an investment in		1,000,000,000			1,000,000,000
Preferred Stock | Loan Originators
Other Assets [Line Items]
Equity method investments		$ 67,800,000			$ 67,800,000