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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Equity method investments - Narrative (Detail)	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
Equity method investments - Narrative (Detail)	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($)	Dec. 31, 2017 Store Location gal	Dec. 31, 2019 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method earnings (losses)	$ 290,000,000	$ 644,000,000		$ 333,000,000	$ 936,000,000
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 fueling locations \| Location						44
Pilot Travel Centers LLC [Member] \| Canadian Provinces [Member]
Schedule of Equity Method Investments [Line Items]
Number of fueling locations \| Location						6
Pilot Travel Centers LLC [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Gallons of fuel purchased annually \| gal						11,000,000,000
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	$ 9,700,000,000			$ 9,700,000,000			$ 10,500,000,000
Equity method investments, carrying value	13,100,000,000			13,100,000,000			13,800,000,000
Equity method earnings (losses)	159,000,000		$ 228,000,000	(180,000,000)	467,000,000
Goodwill and identifiable intangible asset impairment charges from equity method investments				850,000,000	293,000,000
Common stock dividends received				391,000,000	391,000,000
Amount of difference between carrying value and fair value based on quoted market price	$ 3,400,000,000			$ 3,400,000,000
Difference between carrying value and fair value percentage	26.00%			26.00%
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	$ 4,100,000,000			$ 4,100,000,000			$ 3,700,000,000
Equity method earnings (losses)				$ 513,000,000	$ 491,000,000
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%