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Loss And Loss Adjustment Expense Reserves (RMBS Reserves) (Narrative) (Details) (USD $) | 0 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended
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Nov. 30, 2011 | Nov. 30, 2011 | Jun. 30, 2012 | May 31, 2012 | Dec. 31, 2011 | Dec. 31, 2011 RMBS [Member] days | May 31, 2012 RMBS And HELOC And CES [Member] | Nov. 30, 2012 RMBS And HELOC And CES [Member] | Dec. 31, 2011 RMBS And HELOC And CES [Member] | Dec. 31, 2011 Firstlien RMBS [Member] | Dec. 31, 2011 Commercial Mortgage Backed [Member] | Dec. 31, 2011 ALT-A [Member] RMBS And ALT-A [Member] | Dec. 31, 2011 Foreclosure [Member] | Dec. 31, 2011 Real Estate Owned [Member] | Dec. 31, 2011 Bankruptcy [Member]
Loss And Loss Adjustment Expense Reserves [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Charged-off loan recovery value |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |
Delinquency period for fully charged-off loans, days |  |  |  |  |  | 90 |  |  |  |  |  |  |  |  |
Assumed roll rate for ninety plus day delinquent loans |  |  |  |  |  |  |  |  | 95.00% |  |  |  |  |  |
Assumed roll rate for loans |  |  |  |  |  |  |  |  |  |  |  |  | 90.00% | 90.00% | 75.00%
Period of elevated delinquency and loss, beginning, months |  |  |  |  |  |  | 6 |  |  |  |  |  |  |  |
Percentage of loans in 30-59 days delinquent |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |
90+ day roll rate to loss is set |  |  |  |  |  |  |  |  |  | 90.00% |  |  |  |  |
Percentage of loans charged off |  | 30.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of current roll to loss for transaction | 3.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loan severities in certain instances exceded |  |  |  |  |  |  |  |  |  |  | 100.00% |  |  |  |
Decrease in percentage of current roll to loss for transaction |  |  | 0.75% | 25.00% |  |  | 25.00% |  |  |  |  |  |  |  |
Current roll to loss early 2014 |  |  |  |  | 0.00% |  |  |  |  |  |  |  |  |  |
Period of elevated delinquency and loss for stress case, additional months |  |  |  |  |  |  |  | 6 |  |  |  |  |  |  |
Increase to case basis reserves if losses remain at modeled peak levels |  |  |  |  |  |  |  |  | $ 120,000,000 |  |  |  |  |  |
Percentage of loss after declining over a 24 month period |  |  |  |  |  |  |  |  |  |  |  | 25.00% |  |  |

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