Investment Securities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Held-to-maturity
Amortized Cost	$ 21,505	$ 18,877
Unrealized Gains	404	383
Unrealized Losses Other-than-Temporary (d)	(5)	(6)
Unrealized Losses Other (e)	(42)	(38)
Fair Value	21,862	19,216
Available-for-sale securities
Amortized Cost	51,861	51,356
Unrealized Gains	1,413	1,272
Unrealized Losses Other-than-Temporary (d)	(281)	(318)
Unrealized Losses Other (e)	(244)	(373)
Fair Value	52,749	51,937
Other Investments [Member]
Available-for-sale securities
Amortized Cost	217	188
Unrealized Gains	19	15
Unrealized Losses Other (e)		(1)
Fair Value	236	202
U.S. Treasury and agency [Member]
Available-for-sale securities
Amortized Cost	850	1,045
Unrealized Gains	11	13
Unrealized Losses Other (e)		(1)
Fair Value	861	1,057
Obligations of state and political subdivisions [Member]
Available-for-sale securities
Amortized Cost	6,267	6,394
Unrealized Gains	249	167
Unrealized Losses Other (e)	(7)	(22)
Fair Value	6,509	6,539
Obligations of foreign governments [Member]
Available-for-sale securities
Amortized Cost	6	6
Unrealized Gains	0
Fair Value	6	6
Asset backed Securities [Member]
Available-for-sale securities
Amortized Cost	863
Collateralized Debt Obligations [Member]
Available-for-sale securities
Amortized Cost	179	180
Unrealized Gains	33	31
Unrealized Losses Other-than-Temporary (d)	(2)	(3)
Unrealized Losses Other (e)	(4)	(2)
Fair Value	206	206
Other [Member]
Available-for-sale securities
Amortized Cost	684	694
Unrealized Gains	27	16
Unrealized Losses Other-than-Temporary (d)	(5)	(5)
Unrealized Losses Other (e)	(10)	(24)
Fair Value	696	681
Corporate Debt Securities [Member]
Available-for-sale securities
Amortized Cost	1,000	1,000
Unrealized Gains	1	1
Unrealized Losses Other (e)	(116)	(174)
Fair Value	885	827
Perpetual preferred securities [Member]
Available-for-sale securities
Amortized Cost	370	379
Unrealized Gains	33	25
Unrealized Losses Other (e)	(46)	(86)
Fair Value	357	318
Asset backed Securities [Member]
Held-to-maturity
Amortized Cost	57
Collateralized Debt Obligations [Member]
Held-to-maturity
Amortized Cost	35	52
Unrealized Gains	13	13
Unrealized Losses Other (e)		(2)
Fair Value	48	63
Other [Member]
Held-to-maturity
Amortized Cost	22	23
Unrealized Gains	1	1
Unrealized Losses Other-than-Temporary (d)	(5)	(6)
Unrealized Losses Other (e)	(1)	(1)
Fair Value	17	17
Obligations of state and political subdivisions [Member]
Held-to-maturity
Amortized Cost	22	23
Unrealized Gains	2	1
Unrealized Losses Other (e)	(1)	(1)
Fair Value	23	23
Obligations of foreign governments [Member]
Held-to-maturity
Amortized Cost	8	7
Fair Value	8	7
U.S. Treasury and agency [Member]
Held-to-maturity
Amortized Cost	2,559	2,560
Unrealized Gains	29	35
Fair Value	2,588	2,595
Other Debt Securities [Member]
Held-to-maturity
Amortized Cost	120	121
Unrealized Losses Other (e)	(22)	(29)
Fair Value	98	92
Non-agency [Member] \| Average Commercial Non-Agency Mortgage Backed Securities [Member]
Available-for-sale securities
Amortized Cost	41	42
Unrealized Gains	1	2
Unrealized Losses Other (e)	(2)	(2)
Fair Value	40	42
Non-agency [Member] \| Average Commercial Non-Agency Mortgage Backed Securities [Member]
Held-to-maturity
Amortized Cost	4	4
Unrealized Losses Other (e)	(1)	(2)
Fair Value	3	2
Agency [Member] \| Residential [Member]
Available-for-sale securities
Amortized Cost	40,276	39,337
Unrealized Gains	1,017	981
Unrealized Losses Other (e)	(17)	(4)
Fair Value	41,276	40,314
Agency [Member] \| Average Commercial Non-Agency Mortgage Backed Securities [Member]
Available-for-sale securities
Amortized Cost	131	133
Unrealized Gains	7	7
Fair Value	138	140
Agency [Member] \| Residential [Member]
Held-to-maturity
Amortized Cost	18,734	16,085
Unrealized Gains	359	333
Unrealized Losses Other (e)	(17)	(3)
Fair Value	19,076	16,415
Residential Non-agency Prime [Member] \| Residential [Member]
Available-for-sale securities
Amortized Cost	826	911
Unrealized Gains	4	5
Unrealized Losses Other-than-Temporary (d)	(61)	(63)
Unrealized Losses Other (e)	(36)	(50)
Fair Value	733	803
Residential Non-agency Non-Prime [Member] \| Residential [Member]
Available-for-sale securities
Amortized Cost	1,014	1,047
Unrealized Gains	11	9
Unrealized Losses Other-than-Temporary (d)	(213)	(247)
Unrealized Losses Other (e)	(6)	(7)
Fair Value	806	802
Residential Non-agency Non-Prime [Member] \| Residential [Member]
Held-to-maturity
Amortized Cost	1	2
Fair Value	$ 1	$ 2

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For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

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