Investment Income And Gains And Losses (Significant Inputs Used In Measurement Of Credit Loss Component Recognized In Earnings For Each Significant Class Of ABS) (Details)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Expected size of losses, Weighted average	55.40%	[1],[2]	52.20%	[1],[2]	38.44%	[1],[2]
Current subordination levels, Weighted average	1.53%	[2],[3]	4.50%	[2],[3]	9.75%	[2],[3]
Prepayment speed (annual CPR), Weighted average	12.67	[2],[4]	9.45	[2],[4]	6.98	[2],[4]
Minimum [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Expected size of losses, Range	2.48%	[1],[5]	0.21%	[1],[5]	0.00%	[1],[5]
Current subordination levels, Range	0.00%	[3],[5]	0.00%	[3],[5]	0.00%	[3],[5]
Prepayment speed (annual CPR), Range	0.00	[4],[5]	0.00	[4],[5]	0.00	[4],[5]
Maximum [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Expected size of losses, Range	100.00%	[1],[5]	100.00%	[1],[5]	100.00%	[1],[5]
Current subordination levels, Range	35.46%	[3],[5]	42.16%	[3],[5]	48.68%	[3],[5]
Prepayment speed (annual CPR), Range	100.00	[4],[5]	40.20	[4],[5]	36.20	[4],[5]

[1] Represents future expected credit losses on impaired assets expressed as a percentage of total outstanding balance.

[2] Calculated by weighting the relevant input/assumption for each individual security by the outstanding notional of the security.

[3] Represents current level of credit protection (subordination) for the securities, expressed as a percentage of the balance of the collateral group backing the bond.

[4] Values represent high and low points of lifetime vectors of constant prepayment rates.

[5] Represents the range of inputs/assumptions based upon the individual securities within each category.