Credit Enhancement Receivable, Credit Enhancement Deposit and Contingent Liability - Narrative (Details) - USD ($)		3 Months Ended
	Mar. 23, 2021	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Mar. 09, 2021
Credit Enhancement Receivable Contingent Liability And Credit Enhancement Deposit
Credit enhancement receivable		$ 0		$ 0
Deposit in Fannie Mae restricted liquidity account		25,000,000			$ 25,000,000
Returned the credit enhancement deposit	$ 25,000,000
DB Cayman | Credit Risk
Credit Enhancement Receivable Contingent Liability And Credit Enhancement Deposit
Reimbursements under serving agreement		0	$ 0
Percentage of contingent payment					50.00%
Contingent liability		$ 0		$ 0