Investment gains/losses - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Gain (Loss) on Investments [Line Items]
Investment gains/losses	$ 7,553	$ 9,373	$ 3,575
OTTI losses	82	26	697
The Dow Chemical Company [Member] | Conversion of Series A Cumulative Convertible Perpetual Preferred Stock into Common Stock [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	1,200
Preferred Stock [Member] | Wm. Wrigley Jr. Company [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	2,400
Equity Securities [Member] | Tesco PLC [Member]
Gain (Loss) on Investments [Line Items]
OTTI losses			678
Kraft Heinz (previously Heinz Holding) [Member] | Cumulative Compounding Preferred Stock [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	610
Duracell Company [Member] | Common Stock [Member] | Procter & Gamble Company [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	1,100
LSPI and WPLG [Member] | Equity Securities [Member] | PSX and GHC [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses			$ 2,100
Berkshire Hathaway Inc. (Parent) [Member]
Gain (Loss) on Investments [Line Items]
Investment gains/losses	$ 700	6,854
Berkshire Hathaway Inc. (Parent) [Member] | Kraft Heinz (previously Heinz Holding) [Member] | Common Stock [Member]
Gain (Loss) on Investments [Line Items]
Non-cash pre-tax holding gain		$ 6,800