Investments in equity securities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Summary of Investment Holdings [Line Items]
Cost Basis of Investments	$ 49,610	$ 35,544
Unrealized Gains on Investments	28,773	26,641
Unrealized Losses on Investments	(1,392)	(672)
Fair Value of Investments	76,991	61,513
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost Basis of Investments	16,697	15,519
Unrealized Gains on Investments	9,480	9,549
Unrealized Losses on Investments	(1,269)	(454)
Fair Value of Investments	24,908	24,614
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost Basis of Investments	12,390	13,551
Unrealized Gains on Investments	14,320	12,410
Unrealized Losses on Investments		(212)
Fair Value of Investments	26,710	25,749
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost Basis of Investments	20,523	6,474
Unrealized Gains on Investments	4,973	4,682
Unrealized Losses on Investments	(123)	(6)
Fair Value of Investments	$ 25,373	$ 11,150

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

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Reference 2: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

- Definition

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.

+ References+ Details