Expected Loss to be Paid - Liquidation Rates and Key Assumptions in Base Case Expected Loss First Lien RMBS (Details)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Financing Receivable, Modified in Previous 12 Months [Member] | Alt-A and Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	25.00%		35.00%
Financing Receivable, Modified in Previous 12 Months [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	25.00%		35.00%
Financing Receivable, Modified in Previous 12 Months [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	25.00%		35.00%
Financing Receivable, Delinquent in the Previous 12 Months [Member] | Alt-A and Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	25.00%
Financing Receivable, Delinquent in the Previous 12 Months [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	25.00%
Financing Receivable, Delinquent in the Previous 12 Months [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	25.00%
Financing Receivables, 30 to 59 Days Past Due [Member] | Alt-A and Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	35.00%		50.00%		35.00%
Financing Receivables, 30 to 59 Days Past Due [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	40.00%		50.00%		50.00%
Financing Receivables, 30 to 59 Days Past Due [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	35.00%		45.00%		30.00%
Financing Receivables, 60 to 89 Days Past Due [Member] | Alt-A and Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	50.00%		60.00%		55.00%
Financing Receivables, 60 to 89 Days Past Due [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	55.00%		65.00%		65.00%
Financing Receivables, 60 to 89 Days Past Due [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	40.00%		50.00%		45.00%
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Alt-A and Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	60.00%		75.00%		65.00%
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	65.00%		70.00%		75.00%
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	55.00%		60.00%		60.00%
Financing Receivables, Bankruptcy [Member] | Alt-A and Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	45.00%		60.00%		55.00%
Financing Receivables, Bankruptcy [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	50.00%		60.00%		70.00%
Financing Receivables, Bankruptcy [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	40.00%		55.00%		50.00%
Financing Receivable, Foreclosure [Member] | Alt-A and Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	75.00%		85.00%		85.00%
Financing Receivable, Foreclosure [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	80.00%		80.00%		85.00%
Financing Receivable, Foreclosure [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	70.00%		70.00%		80.00%
Financing Receivable, Real Estate Owned [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liquidation Rate	100.00%		100.00%		100.00%
United States [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Period until intermediate CDR			48 months		36 months
United States [Member] | Subprime [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Period until intermediate CDR	48 months
Final CPR	15.00%	[1],[2]	15.00%	[1],[2]	15.00%	[1],[2]
United States [Member] | Subprime [Member] | 2005 and prior [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	75.00%		90.00%		90.00%
United States [Member] | Subprime [Member] | 2006 [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	90.00%		90.00%		90.00%
United States [Member] | Subprime [Member] | 2007 [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	90.00%		90.00%		90.00%
United States [Member] | Subprime [Member] | Minimum [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	4.90%	[1]	5.60%	[1]	7.30%	[1]
Intermediate CDR	1.00%	[1]	1.10%	[1]	1.50%	[1]
Final CDR	0.20%	[1]	0.30%	[1]	0.40%	[1]
Initial CPR	0.00%	[1]	0.00%	[1]	0.00%	[1]
United States [Member] | Subprime [Member] | Maximum [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	15.00%	[1]	16.20%	[1]	26.20%	[1]
Intermediate CDR	3.00%	[1]	3.20%	[1]	5.20%	[1]
Final CDR	0.70%	[1]	0.80%	[1]	1.30%	[1]
Initial CPR	10.50%	[1]	15.70%	[1]	17.60%	[1]
United States [Member] | Subprime [Member] | Weighted Average [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	10.60%		11.80%		17.30%
Intermediate CDR	2.10%		2.40%		3.50%
Final CDR	0.40%		0.40%		0.60%
Initial CPR	6.10%		4.10%		3.60%
United States [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Period until intermediate CDR			48 months		36 months
United States [Member] | Option ARM [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Period until intermediate CDR	48 months
Final CPR	15.00%	[1]	15.00%	[1]	15.00%	[1]
United States [Member] | Option ARM [Member] | 2005 and prior [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	60.00%		65.00%		65.00%
United States [Member] | Option ARM [Member] | 2006 [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	70.00%		65.00%		65.00%
United States [Member] | Option ARM [Member] | 2007 [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	65.00%		65.00%		65.00%
United States [Member] | Option ARM [Member] | Minimum [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	4.30%	[1]	4.90%	[1]	7.00%	[1]
Intermediate CDR	0.90%	[1]	1.00%	[1]	1.40%	[1]
Final CDR	0.20%	[1]	0.20%	[1]	0.40%	[1]
Initial CPR	1.10%	[1]	0.40%	[1]	0.00%	[1]
United States [Member] | Option ARM [Member] | Maximum [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	14.20%	[1]	16.80%	[1]	26.10%	[1]
Intermediate CDR	2.80%	[1]	3.40%	[1]	5.20%	[1]
Final CDR	0.70%	[1]	0.80%	[1]	1.30%	[1]
Initial CPR	11.80%	[1]	13.10%	[1]	10.70%	[1]
United States [Member] | Option ARM [Member] | Weighted Average [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	10.60%		11.90%		18.40%
Intermediate CDR	2.10%		2.40%		3.70%
Final CDR	0.50%		0.50%		0.80%
Initial CPR	4.90%		4.70%		4.00%
United States [Member] | Alt-A [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Period until intermediate CDR	48 months		48 months		36 months
Final CPR	15.00%	[1]	15.00%	[1]	15.00%	[1]
United States [Member] | Alt-A [Member] | 2005 and prior [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	60.00%		65.00%		65.00%
United States [Member] | Alt-A [Member] | 2006 [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	70.00%		65.00%		65.00%
United States [Member] | Alt-A [Member] | 2007 [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial loss severity	65.00%		65.00%		65.00%
United States [Member] | Alt-A [Member] | Minimum [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	2.00%	[1]	2.80%	[1]	3.80%	[1]
Intermediate CDR	0.40%	[1]	0.60%	[1]	0.80%	[1]
Final CDR	0.10%	[1]	0.10%	[1]	0.20%	[1]
Initial CPR	1.70%	[1]	0.00%	[1]	0.00%	[1]
United States [Member] | Alt-A [Member] | Maximum [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	13.40%	[1]	18.40%	[1]	23.20%	[1]
Intermediate CDR	2.70%	[1]	3.70%	[1]	4.60%	[1]
Final CDR	0.70%	[1]	0.90%	[1]	1.20%	[1]
Initial CPR	21.00%	[1]	34.20%	[1]	39.40%	[1]
United States [Member] | Alt-A [Member] | Weighted Average [Member] | RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	7.30%		9.70%		13.30%
Intermediate CDR	1.50%		1.90%		2.70%
Final CDR	0.30%		0.50%		0.60%
Initial CPR	7.70%		9.70%		7.40%

[1] Represents variables for most heavily weighted scenario (the “base case”).

[2] For transactions where the initial CPR is higher than the final CPR, the initial CPR is held constant and the final CPR is not used.