Securities Available for Sale, Other-Than-Temporary Impaired Debt Securities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	$ 256	$ 541	$ 692
Debt Securities [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	240	423	672
Total changes to OCI for non-credit-related OTTI	(237)	(74)	(172)
Total OTTI losses recorded on debt securities	3	349	500
Debt Securities [Member] \| Credit-related OTTI [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	237	422	400
Debt Securities [Member] \| Intent-to-sell OTTI [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	3	1	272
US States and Political Subdivisions [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	16	2	16
Total changes to OCI for non-credit-related OTTI	1	(1)	(4)
Residential [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	84	252	175
Total changes to OCI for non-credit-related OTTI	(178)	(171)	(326)
Commercial [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	86	101	120
Total changes to OCI for non-credit-related OTTI	(88)	105	138
Collateralized debt obligations [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	1	1	15
Total changes to OCI for non-credit-related OTTI	(1)	4	54
Other Debt Securities [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	42	64	69
Total changes to OCI for non-credit-related OTTI	28	(13)	(33)
Corporate debt securities [Member]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities [Abstract]
Total OTTI recorded as part of gross realized losses	11	3	10
Total changes to OCI for non-credit-related OTTI	$ 1	$ 2	$ (1)

The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References+ Details

The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

+ References+ Details