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Equity method investments - Narrative (Detail)		12 Months Ended
Equity method investments - Narrative (Detail)	Oct. 03, 2017 USD ($) Employee Location	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage		20.00%
Equity method earnings (losses)		$ 1,176,000,000	$ (2,167,000,000)	$ 3,014,000,000
Berkshire Hathaway Inc. (Parent) [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments, carrying value		13,757,000,000	13,813,000,000
Equity method earnings (losses)		$ 493,000,000	(2,730,000,000)	2,938,000,000
Pilot Travel Centers LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of locations \| Location	750
Pilot Travel Centers LLC [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Number of team members \| Employee	28,000
Pilot Travel Centers LLC [Member] \| Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Annual revenues	$ 30,000,000,000
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
Equity method investment ownership percentage		26.60%
Equity method investments, fair value		$ 10,500,000,000	14,000,000,000.0
Equity method investments, carrying value		13,800,000,000	13,800,000,000
Equity method earnings (losses)		493,000,000	(2,700,000,000)	2,900,000,000
Impairment loss on equity investment		1,900,000,000	15,900,000,000
Common stock dividends received		521,000,000	814,000,000	797,000,000
Amount of difference between carrying value and fair value based on quoted market price		$ 3,300,000,000
Difference between carrying value and fair value percentage		(24.00%)
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		$ 3,700,000,000	3,500,000,000
Equity method earnings (losses)		$ 683,000,000	$ 563,000,000	$ 76,000,000
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%