Investments in equity securities (Detail) - USD ($) $ in Millions	Dec. 31, 2015		Dec. 31, 2014
Summary of Investment Holdings [Line Items]
Cost basis of investments	$ 62,310		$ 58,370
Unrealized gains on investments	52,772		60,137
Unrealized losses on investments	(3,260)		(1,037)
Fair value of investments	111,822	[1]	117,470	[2]
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	20,026		22,495
Unrealized gains on investments	27,965		33,170
Unrealized losses on investments	(21)
Fair value of investments	47,970		55,665
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	6,867		6,951
Unrealized gains on investments	18,022		18,389
Unrealized losses on investments	(1)		(1)
Fair value of investments	24,888		25,339
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	35,417		28,924
Unrealized gains on investments	6,785		8,578
Unrealized losses on investments	(3,238)		(1,036)
Fair value of investments	$ 38,964		$ 36,466

[1] 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 ("IBM")-$11.2 billion; and The Coca-Cola Company-$17.2 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).