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Residential Whole Loans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Receivables [Abstract]
Total residential whole loans	$ 5,300,000,000	$ 7,400,000,000
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loss on sale of financing receivable	(800,000)
Interest income	0
Unpaid principal balance	24,100,000
Non-QM Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, sale	1,800,000,000
Loss on sale of financing receivable	273,000,000.0
Purchased Performing Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	373,300,000	$ 99,900,000
Purchased Credit Deteriorated Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	151,400,000
Without Associated Credit Losses
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual	$ 130,700,000

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Amount of interest income on financing receivable on nonaccrual status.

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-Publisher FASB
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