Loss And Loss Adjustment Expense Reserves (RMBS Reserves) (Narrative) (Details) (USD $)	0 Months Ended	6 Months Ended	9 Months Ended						1 Months Ended	9 Months Ended
	Aug. 31, 2011	Mar. 31, 2012	Sep. 30, 2011	Sep. 30, 2011 Foreclosure [Member]	Sep. 30, 2011 Real Estate Owned [Member]	Sep. 30, 2011 Bankruptcy [Member]	Sep. 30, 2011 ALT-A [Member] RMBS And ALT-A [Member]	Sep. 30, 2011 RMBS [Member]	Aug. 31, 2011 RMBS And HELOC And CES [Member]	Sep. 30, 2011 RMBS And HELOC And CES [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										100.00%
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 day delinquent bucket	10.00%
Percentage of loans charged off	30.00%
Percentage of current roll to loss for transaction	3.00%
Decrease in percentage of current roll to loss for transaction	25.00%	0.75%							25.00%
Current roll to loss by 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 peak levels for six additional months										$ 110,000,000
Percentage of loss after declining over a 24 month period							25.00%