Expected Loss to be Paid (Recovered) - Key Assumptions in Base Scenario Expected Loss First Lien RMBS (Details) - RMBS - United States	3 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Schedule of Expected Losses to be Paid [Line Items]
Loss severity on future defaults			50.00%
Base Scenario | First Lien
Schedule of Expected Losses to be Paid [Line Items]
Percent of deferred loan balances to be recovered	50.00%	30.00%	30.00%
Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Loss severity on future defaults	98.00%		98.00%
Projected future recoveries on previously charged-off loans	50.00%		40.00%
Current but recently delinquent | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Liquidation rate	20.00%		20.00%
30 – 59 Days Delinquent | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Liquidation rate	30.00%		30.00%
60 – 89 Days Delinquent | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Liquidation rate	30.00%		40.00%
90+ Days Delinquent | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Liquidation rate	40.00%		60.00%
Bankruptcy | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Liquidation rate	55.00%		55.00%
Foreclosure | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Liquidation rate	40.00%		55.00%
Real Estate Owned | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Liquidation rate	100.00%		100.00%
Minimum
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	0.00%		0.00%
Final CDR	0.00%		0.00%
Loss severity on future defaults	40.00%
Minimum | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	0.40%		0.00%
Final CDR	0.00%		0.00%
Maximum
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	13.50%		10.00%
Final CDR	0.70%		0.50%
Loss severity on future defaults	50.00%
Maximum | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	5.00%		9.30%
Final CDR	0.20%		0.50%
Weighted Average
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	3.40%		4.20%
Final CDR	0.20%		0.20%
Loss severity on future defaults	43.10%
Weighted Average | Home Equity Line of Credit
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	2.30%		2.60%
Final CDR	0.10%		0.10%