Investments in equity securities (Detail) - USD ($) $ in Millions	Jun. 30, 2015		Dec. 31, 2014
Summary of Investment Holdings [Line Items]
Cost basis of investments	$ 61,832		$ 58,370
Unrealized gains on investments	56,868		60,137
Unrealized losses on investments	(978)		(1,037)
Fair value of investments	117,722	[1]	117,470	[2]
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	23,388		22,495
Unrealized gains on investments	31,312		33,170
Unrealized losses on investments	(2)
Fair value of investments	54,698		55,665
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	6,908		6,951
Unrealized gains on investments	16,710		18,389
Unrealized losses on investments	(2)		(1)
Fair value of investments	23,616		25,339
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	31,536		28,924
Unrealized gains on investments	8,846		8,578
Unrealized losses on investments	(974)		(1,036)
Fair value of investments	$ 39,408		$ 36,466

[1] Approximately 58% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company - $11.8 billion; Wells Fargo & Company - $27.6 billion; International Business Machines Corporation - $12.9 billion; and The Coca-Cola Company - $15.7 billion).

[2] Approximately 59% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company - $14.1 billion; Wells Fargo & Company - $26.5 billion; International Business Machines Corporation - $12.3 billion; and The Coca-Cola Company - $16.9 billion).