Loss And Loss Adjustment Expense Reserves (RMBS Reserves) (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended
	May 31, 2013	Jun. 30, 2013
Loss And Loss Adjustment Expense Reserves [Line Items]
Charged-off loans recovery values		$ 0
Percentage of Current Roll to Loss for the transaction		3.00%
June Two Thousand Thirteen To November Two Thousand Thirteen [Member] | Scenario Forecast [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Decrease in percentage of Current Roll to Loss for transaction		25.00%
June Two Thousand Thirteen To November Two Thousand Thirteen [Member] | Scenario Forecast [Member] | Rate Reduction [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Decrease in percentage of Current Roll to Loss for transaction		0.75%
December Thirty One Two Thousand Thirteen To June Thirty Two Thousand Fourteen [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Current Roll to Loss		0.00%
First Lien R M B S 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 R M B S 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 R M B S Reserves [Member] | Foreclosure [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Assumed roll rate for loans		90.00%
First Lien R M B S Reserves [Member] | Real Estate Owned [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Assumed roll rate for loans		90.00%
First Lien R M B S Reserves [Member] | Bankruptcy [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Assumed roll rate for loans		75.00%
Rmbs And Heloc And Ces [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Assumed roll rate for ninety plus day delinquent loans excluding foreclosure 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		90
Change in recoveries of actual and expected payments related to ineligible mortgages		$ 308
Rmbs And Heloc And Ces [Member] | Scenario Forecast [Member] | Minimum [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] | Scenario Forecast [Member] | Maximum [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Period of elevated delinquency and loss for stress case, additional months		24
Rmbs And Heloc And Ces [Member] | June Two Thousand Thirteen To November Two Thousand Thirteen [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Period of elevated delinquency and loss for base case, beginning, months		6