Investments in equity securities (Detail) - USD ($) $ in Millions	Jun. 30, 2017		Dec. 31, 2016
Summary of Investment Holdings [Line Items]
Cost basis of investments	$ 71,922		$ 66,377
Unrealized gains on investments	65,967		56,365
Unrealized losses on investments	(776)		(710)
Fair value of investments	137,113	[1]	122,032	[2]
Banks, insurance and finance [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	20,887		19,852
Unrealized gains on investments	32,754		30,572
Fair value of investments	53,641		50,424
Consumer products [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	19,495		10,657
Unrealized gains on investments	22,267		16,760
Unrealized losses on investments			(9)
Fair value of investments	41,762		27,408
Commercial, industrial and other [Member]
Summary of Investment Holdings [Line Items]
Cost basis of investments	31,540		35,868
Unrealized gains on investments	10,946		9,033
Unrealized losses on investments	(776)		(701)
Fair value of investments	$ 41,710		$ 44,200

[1] Approximately 62% of the aggregate fair value was concentrated in the equity securities of five companies: American Express Company - $12.8 billion, Apple Inc. - $19.4 billion, The Coca-Cola Company - $17.9 billion, International Business Machines Corporation ("IBM") - $8.3 billion and Wells Fargo & Company - $27.3 billion.

[2] Approximately 62% of the aggregate fair value was concentrated in the equity securities of five companies: American Express Company - $11.2 billion, Apple Inc. - $7.1 billion, The Coca-Cola Company - $16.6 billion, IBM - $13.5 billion and Wells Fargo & Company - $27.6 billion.