Significant business acquisitions - Narrative (Detail) $ in Millions				3 Months Ended			8 Months Ended	9 Months Ended
	Sep. 01, 2023 USD ($)	Jan. 31, 2023 USD ($)	Oct. 19, 2022 USD ($)	Sep. 30, 2023 USD ($) Location Store	Mar. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) Location Store	Sep. 30, 2023 USD ($) Location Store	Sep. 30, 2022 USD ($)	Aug. 31, 2023
Business Acquisition [Line Items]
Revenues				$ 65,197		$ 53,306		$ 190,325	$ 155,665
Net earnings attributable to Berkshire shareholders				(12,767)		(2,798)		58,649	(40,839)
Equity method earnings				$ 262		$ 415		$ 1,461	$ 958
Pilot Travel Centers LLC [Member]
Business Acquisition [Line Items]
Percentage of additional interest acquired		41.40%
Business acquisition, cash consideration		$ 8,200
Economic interest		38.60%		38.60%			38.60%	38.60%
Revenues							$ 37,400
Net earnings attributable to Berkshire shareholders							$ 380
One-time, non-cash remeasurement gain recognized					$ 3,000
Pilot Travel Centers LLC [Member] | Canadian Provinces [Member] | Travel Center Locations [Member]
Business Acquisition [Line Items]
Number of places retail locations located | Location				6			6	6
Pilot Travel Centers LLC [Member] | States [Member] | Travel Center Locations [Member]
Business Acquisition [Line Items]
Number of places retail locations located | Location				44			44	44
Pilot Travel Centers LLC [Member] | U.S. and Canada [Member] | Travel Center Locations [Member] | Minimum [Member]
Business Acquisition [Line Items]
Number of retail | Store				750			750	750
Alleghany Corporation [Member]
Business Acquisition [Line Items]
Business acquisition, cash consideration			$ 11,500
Business acquisition, effective date of acquisition			Oct. 19, 2022
Cove Point LNG LP [Member] | Berkshire Hathaway Energy [Member]
Business Acquisition [Line Items]
Business acquisition, cash consideration	$ 3,300
Business acquisition, effective date of acquisition	Sep. 01, 2023
Excess consideration paid for acquiring noncontrolling Interest	$ 667
Cove Point LNG LP [Member] | Limited Partner [Member] | Berkshire Hathaway Energy [Member]
Business Acquisition [Line Items]
Percentage of additional interest acquired	50.00%
Economic interest										25.00%
Economic interest	75.00%
Cove Point LNG LP [Member] | Variable Interest Entity, Primary Beneficiary [Member] | General Partner [Member] | Berkshire Hathaway Energy [Member]
Business Acquisition [Line Items]
Economic interest	100.00%