Loss And Loss Adjustment Expense Reserves (RMBS Reserves) (Narrative) (Detail) (USD $)	1 Months Ended	3 Months Ended
	Feb. 28, 2013	Mar. 31, 2013
Loss And Loss Adjustment Expense Reserves [Line Items]
Charged-off loans recovery values		$ 0
March 2013 to August 2013 [Member] | Scenario, Forecast [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Decrease in percentage of Current Roll to Loss for transaction		25.00%
March 2013 to August 2013 [Member] | Linear reduction in original value [Member] | Scenario, Forecast [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Decrease in percentage of Current Roll to Loss for transaction		0.75%
September 30, 2013 to June 30, 2014 [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Current Roll to Loss		0.00%
RMBS And HELOC And CES [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Assumed roll rate for ninety plus day delinquent loans excluding foreclosures and Real Estate Owned		95.00%
Percentage of loans in 30-59 days delinquent bucket	10.00%
Percentage of loans charged-off	30.00%
Percentage of Current Roll to Loss for the transaction	3.00%
Addition to case basis reserves before considering potential recoveries for elevated delinquency and loss for stress case		80,000,000
Change in recoveries of actual and expected payments related to ineligible mortgages		$ 306,000,000
RMBS And HELOC And CES [Member] | March 2013 to August 2013 [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Period of elevated delinquency and loss base case, beginning, months		6
RMBS And HELOC And CES [Member] | March 2013 to August 2013 [Member] | Minimum [Member] | Scenario, Forecast [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Period of elevated delinquency and loss for stress case, additional months		6
RMBS And HELOC And CES [Member] | March 2013 to August 2013 [Member] | Maximum [Member] | Scenario, Forecast [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Period of elevated delinquency and loss for stress case, additional months		24
First-Lien RMBS Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Delinquency period charged off on transaction specific basis, days		90
90+ day roll rate to loss set		90.00%
First-Lien RMBS Reserves [Member] | Alt-A [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Percentage of loss after declining over a 24-month period		25.00%
First-Lien RMBS Reserves [Member] | Foreclosure [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Assumed roll rate for loans		90.00%
First-Lien RMBS Reserves [Member] | Real Estate Owned [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Assumed roll rate for loans		90.00%
First-Lien RMBS Reserves [Member] | Bankruptcy [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Assumed roll rate for loans		75.00%