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Equity method investments - Narrative (Detail)	3 Months Ended		12 Months Ended
Equity method investments - Narrative (Detail)	Mar. 31, 2021 USD ($) Store Location shares	Mar. 31, 2020 USD ($)	Dec. 31, 2017	Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method earnings	$ 251,000,000	$ 300,000,000
Pilot Travel Centers LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of retail \| Store	950
Pilot Travel Centers LLC [Member] \| U.S. States [Member]
Schedule of Equity Method Investments [Line Items]
Number of places retail locations located \| Location	44
Pilot Travel Centers LLC [Member] \| Canadian Provinces [Member]
Schedule of Equity Method Investments [Line Items]
Number of places retail locations located \| Location	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
Equity method investment ownership percentage	26.60%
Equity method investments, fair value	$ 13,000,000,000.0			$ 11,300,000,000
Equity method investments, carrying value	13,400,000,000			13,300,000,000
Equity method earnings	150,000,000	101,000,000
Common stock dividends received	130,000,000	130,000,000
Amount of difference between carrying value and fair value based on quoted market price	$ 362,000,000
Difference between carrying value and fair value percentage	2.70%
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	$ 3,100,000,000			$ 4,000,000,000.0
Equity method earnings	101,000,000	$ 199,000,000
Equity method investment distributions from other investees	896,000,000
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%
Commercial paper outstanding	$ 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
Berkadia Commercial Mortgage LLC [Member] \| Jefferies Financial Group Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage	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%
Electric Transmission Texas, LLC [Member] \| American Electric Power [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage	50.00%