Investments in equity securities (Detail) - USD ($) $ in Millions	Sep. 30, 2016		Dec. 31, 2015
Summary of Investment Holdings [Line Items]
Cost basis of investments	$ 57,518		$ 62,310
Unrealized gains on investments	46,389		52,772
Unrealized losses on investments	(1,372)		(3,260)
Fair value of investments	102,535	[1]	111,822	[2]
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	19,852		20,026
Unrealized gains on investments	21,695		27,965
Unrealized losses on investments	(173)		(21)
Fair value of investments	41,374		47,970
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	5,149		6,867
Unrealized gains on investments	16,790		18,022
Unrealized losses on investments			(1)
Fair value of investments	21,939		24,888
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	32,517		35,417
Unrealized gains on investments	7,904		6,785
Unrealized losses on investments	(1,199)		(3,238)
Fair value of investments	$ 39,222		$ 38,964

[1] Approximately 60% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company - $9.7 billion; Wells Fargo & Company - $22.1 billion; International Business Machines Corporation ("IBM") - $12.9 billion; and The Coca-Cola Company - $16.9 billion).

[2] Approximately 59% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company - $10.5 billion; Wells Fargo & Company - $27.2 billion; IBM - $11.2 billion; and The Coca-Cola Company - $17.2 billion).