Investments in equity securities (Detail) - USD ($) $ in Millions	Mar. 31, 2016		Dec. 31, 2015
Summary of Investment Holdings [Line Items]
Cost basis of investments	$ 59,714		$ 62,310
Unrealized gains on investments	48,825		52,772
Unrealized losses on investments	(2,119)		(3,260)
Fair value of investments	106,420	[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	22,806		27,965
Unrealized losses on investments	(150)		(21)
Fair value of investments	42,508		47,970
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	4,709		6,867
Unrealized gains on investments	18,323		18,022
Unrealized losses on investments			(1)
Fair value of investments	23,032		24,888
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	35,153		35,417
Unrealized gains on investments	7,696		6,785
Unrealized losses on investments	(1,969)		(3,238)
Fair value of investments	$ 40,880		$ 38,964

[1] Approximately 60% of the aggregate fair value was concentrated in the equity securities of four companies (American Express Company - $9.3 billion; Wells Fargo & Company - $24.2 billion; International Business Machines Corporation ("IBM") - $12.3 billion; and The Coca-Cola Company - $18.6 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; International Business Machines Corporation - $11.2 billion; and The Coca-Cola Company - $17.2 billion).