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Equity method investments - Narrative (Detail)	3 Months Ended			6 Months Ended		12 Months Ended
Equity method investments - Narrative (Detail)	Jun. 30, 2021 USD ($) Store Location shares	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) Store Location shares	Jun. 30, 2020 USD ($)	Dec. 31, 2017	Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method earnings (losses)	$ 147,000,000		$ (257,000,000)	$ 398,000,000	$ 43,000,000
Pilot Travel Centers LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of retail \| Store	1,000			1,000
Pilot Travel Centers LLC [Member] \| U.S. States [Member]
Schedule of Equity Method Investments [Line Items]
Number of places retail locations located \| Location	44			44
Pilot Travel Centers LLC [Member] \| Canadian Provinces [Member]
Schedule of Equity Method Investments [Line Items]
Number of places retail locations located \| Location	6			6
Pilot Travel Centers LLC [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage						38.60%
Pilot Travel Centers LLC [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Agreement to Acquire Additional Interest in 2023 [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of additional interest to be acquired				41.40%
Haslam Family [Member] \| Pilot Travel Centers LLC [Member]
Schedule of Equity Method Investments [Line Items]
Majority ownership percentage				50.10%
Haslam Family [Member] \| Pilot Travel Centers LLC [Member] \| Agreement to Acquire Additional Interest in 2023 [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage				20.00%
Third Party [Member] \| Pilot Travel Centers LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage				11.30%
The Kraft Heinz Company [Member]
Schedule of Equity Method Investments [Line Items]
Number of shares owned \| shares	325,442,152			325,442,152
Equity method investment ownership percentage	26.60%			26.60%
Equity method investments, fair value	$ 13,300,000,000			$ 13,300,000,000			$ 11,300,000,000
Equity method investments, carrying value	13,300,000,000			13,300,000,000			13,300,000,000
Equity method earnings (losses)	(7,000,000)		(440,000,000)	143,000,000	(339,000,000)
Impairment charges on equity investment			$ 700,000,000		750,000,000
Common stock dividends received				260,000,000	260,000,000
Berkadia Commercial Mortgage LLC, Pilot Travel Centers LLC, and Electric Transmission Texas, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments, carrying value	$ 3,200,000,000			3,200,000,000			$ 4,000,000,000.0
Equity method earnings (losses)				255,000,000	$ 382,000,000
Equity method investment distributions from other investees				$ 982,000,000
Pilot Travel Centers LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment non-recurring distribution		$ 849,000,000
Berkadia Commercial Mortgage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage	50.00%			50.00%
Commercial paper outstanding	$ 1,470,000,000			$ 1,470,000,000
Berkadia Commercial Mortgage LLC [Member] \| Commercial Paper [Member]
Schedule of Equity Method Investments [Line Items]
Maximum outstanding balance of commercial paper borrowings	$ 1,500,000,000			$ 1,500,000,000
Berkadia Commercial Mortgage LLC [Member] \| Jefferies Financial Group Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage	50.00%			50.00%
Electric Transmission Texas, LLC [Member] \| Berkshire Hathaway Energy Company Subsidiary [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage	50.00%			50.00%
Electric Transmission Texas, LLC [Member] \| American Electric Power [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage	50.00%			50.00%