Expected Loss to be Paid - Key Assumptions in Base Case Expected Loss Second Lien RMBS (Details) (RMBS [Member], United States [Member])	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Expected period until final CDR	34 months	[1]	34 months	[1]	36 months	[1]
Final CPR			10.00%	[1],[2]	10.00%	[1],[2]
Loss severity			98.00%	[1]	98.00%	[1]
HELOCs [Member] | Minimum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	2.80%	[1]	2.30%	[1]	3.80%	[1]
Final CDR trended down to	0.50%	[1]	0.40%	[1]	0.40%	[1]
Initial CPR	6.90%	[1]	2.70%	[1]	2.90%	[1]
Final CPR	15.00%	[1],[2]
Loss severity	90.00%	[1]
HELOCs [Member] | Maximum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	6.80%	[1]	7.70%	[1]	15.90%	[1]
Final CDR trended down to	3.20%	[1]	3.20%	[1]	3.20%	[1]
Initial CPR	21.80%	[1]	21.50%	[1]	15.40%	[1]
Final CPR	21.80%	[1],[2]
Loss severity	98.00%	[1]
HELOCs [Member] | Weighted Average [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	4.10%	[1]	4.90%	[1]	8.80%	[1]
Final CDR trended down to	1.20%	[1]	1.10%	[1]	1.20%	[1]
Initial CPR	11.00%	[1]	9.90%	[1]	6.60%	[1]
Final CPR	15.50%	[1],[2]
Loss severity	90.40%	[1]
Closed-end [Member]
Schedule of Expected Losses to be Paid [Line Items]
Expected period until final CDR	34 months	[1]	34 months	[1]	36 months	[1]
Final CPR	15.00%	[1],[2]	10.00%	[1],[2]	10.00%	[1],[2]
Loss severity	98.00%	[1]	98.00%	[1]	98.00%	[1]
Closed-end [Member] | Minimum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	5.50%	[1]	7.30%	[1]	7.30%	[1]
Final CDR trended down to	3.50%	[1]	3.50%	[1]	3.50%	[1]
Initial CPR	2.80%	[1]	3.10%	[1]	1.90%	[1]
Closed-end [Member] | Maximum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	12.50%	[1]	15.10%	[1]	20.70%	[1]
Final CDR trended down to	9.10%	[1]	9.10%	[1]	9.10%	[1]
Initial CPR	13.90%	[1]	12.00%	[1]	12.50%	[1]
Closed-end [Member] | Weighted Average [Member]
Schedule of Expected Losses to be Paid [Line Items]
Plateau CDR	7.20%	[1]	8.50%	[1]	12.70%	[1]
Final CDR trended down to	4.90%	[1]	5.00%	[1]	4.90%	[1]
Initial CPR	9.90%	[1]	7.10%	[1]	4.00%	[1]

[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.