Fair Values (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investment securities:
Equity securities	$ 296	$ 360
Debt securities and other	5,318	6,787
Derivative assets	942	1,516
Total assets	6,556	8,663
Level 1 [Member]
Investment securities:
Equity securities	296	360
Debt securities and other	338	340
Derivative assets	0	0
Total assets	634	700
Level 2 [Member]
Investment securities:
Equity securities	0	0
Debt securities and other	4,980	6,447
Derivative assets	942	1,516
Total assets	5,922	7,963
Level 3 [Member]
Investment securities:
Total assets	$ 0	$ 0

Amount of equity securities categorized neither as held-to-maturity nor as trading.

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details