Significant business acquisitions and other transactions - Narrative (Detail) $ in Millions					1 Months Ended		2 Months Ended	3 Months Ended
		Sep. 01, 2023 USD ($)	Jan. 31, 2023 USD ($)	Oct. 19, 2022 USD ($)	Sep. 30, 2024 USD ($)	Jan. 31, 2024 USD ($)	Oct. 31, 2024 USD ($) shares	Mar. 31, 2023 USD ($)	Dec. 31, 2024 USD ($) Location	Dec. 31, 2023 USD ($)	Aug. 31, 2023	Dec. 31, 2022 USD ($)
Business Acquisition [Line Items]
Goodwill	[1]								$ 83,880	$ 84,626		$ 78,119
Berkshire Hathaway Energy ("BHE") [Member]
Business Acquisition [Line Items]
Consideration for repurchase of common stock held by noncontrolling shareholders					$ 2,900
Percentage of outstanding common stock repurchased					5.85%
Alleghany Corporation [Member]
Business Acquisition [Line Items]
Acquired assets				$ 35,600
Business acquisition, effective date of acquisition				Oct. 19, 2022
Business acquisition, cash consideration				$ 11,500
Liabilities				24,100
Unpaid losses and loss adjustment expenses				15,100
Cash and investments				19,700
Goodwill				$ 3,900
Pilot Travel Centers LLC [Member]
Business Acquisition [Line Items]
Percentage of additional interest acquired			41.40%
Acquired assets			$ 28,520
Business acquisition, cash consideration			8,200			$ 2,600
Liabilities			$ 10,794
Economic interest			38.60%							38.60%
Economic interest after subsequent acquisition			80.00%			100.00%
Goodwill			$ 6,605
One-time, non-cash remeasurement gain recognized								$ 3,000
Adjustments to additional paid in capital						$ 517
Pilot Travel Centers LLC [Member] | Canadian Provinces [Member]
Business Acquisition [Line Items]
Number of places retail locations located | Location									5
Cove Point LNG LP [Member] | Berkshire Hathaway Energy ("BHE") [Member]
Business Acquisition [Line Items]
Business acquisition, effective date of acquisition		Sep. 01, 2023
Business acquisition, cash consideration		$ 3,300
Adjustments to additional paid in capital		$ 667
Cove Point LNG LP [Member] | General Partner [Member] | Cove Point [Member] | Berkshire Hathaway Energy ("BHE") [Member]
Business Acquisition [Line Items]
Economic interest		100.00%
Cove Point LNG LP [Member] | Limited Partner [Member] | Berkshire Hathaway Energy ("BHE") [Member]
Business Acquisition [Line Items]
Percentage of additional interest acquired		50.00%
Economic interest											25.00%
Economic interest after subsequent acquisition		75.00%
BHE [Member] | Common Class B [Member]
Business Acquisition [Line Items]
Number of shares exchanged | shares							2,291,631
Value of shares exchanged							$ 1,045
Berkshire Hathaway Inc. (Parent) [Member] | BHE [Member]
Business Acquisition [Line Items]
Percentage of outstanding common stock purchased							2.12%

[1] Net of accumulated goodwill impairments of $11.5 billion as of December 31, 2024, $11.1 billion as of December 31, 2023 and $11.0 billion as of December 31, 2022.