Investments in equity securities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Summary of Investment Holdings [Line Items]
Cost basis of investments	$ 59,607		$ 59,451
Unrealized gains on investments	59,951		58,197
Unrealized losses on investments	(366)		(143)
Fair value of investments	119,192	[1]	117,505	[2]
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	22,368		22,420
Unrealized gains on investments	32,190		28,021
Fair value of investments	54,558		50,441
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	7,088		7,082
Unrealized gains on investments	18,129		17,854
Unrealized losses on investments	(1)
Fair value of investments	25,216		24,936
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	30,151		29,949
Unrealized gains on investments	9,632		12,322
Unrealized losses on investments	(365)		(143)
Fair value of investments	$ 39,418		$ 42,128

[1] As of June 30, 2014, approximately 58% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company - $14.4 billion; Wells Fargo & Company - $25.4 billion; International Business Machines Corporation - $12.7 billion; and The Coca-Cola Company - $16.9 billion).

[2] As of December 31, 2013, approximately 55% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company - $13.8 billion; Wells Fargo & Company - $21.9 billion; International Business Machines Corporation - $12.8 billion; and The Coca-Cola Company - $16.5 billion).