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Equity method investments - Narrative (Detail)		3 Months Ended		6 Months Ended	9 Months Ended
Equity method investments - Narrative (Detail)	Oct. 03, 2017	Sep. 30, 2019 USD ($) Employee Location shares	Sep. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) Employee Location shares	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method earnings		$ 644,000,000	$ 316,000,000		$ 936,000,000	$ 1,044,000,000
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member]
Schedule of Equity Method Investments [Line Items]
Number of locations \| Location		750			750
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Number of team members \| Employee		28,000			28,000
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Annual revenues					$ 30,000,000,000
Pilot Travel Centers LLC, d/b/a Pilot Flying J [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	38.60%
Pilot Travel Centers LLC, d/b/a Pilot Flying J [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, d/b/a Pilot Flying J [Member]
Schedule of Equity Method Investments [Line Items]
Majority ownership percentage					50.10%
Haslam Family [Member] \| Pilot Travel Centers LLC, d/b/a Pilot Flying J [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, d/b/a Pilot Flying J [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		$ 9,100,000,000			$ 9,100,000,000		$ 14,000,000,000.0
Equity method investments, carrying value		$ 13,800,000,000			13,800,000,000		13,800,000,000
Equity method earnings			$ 168,000,000	$ 228,000,000	467,000,000	635,000,000
Dividends received					$ 391,000,000	610,000,000
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%
Berkadia Commercial Mortgage LLC [Member] \| Jefferies Financial Group Inc. [Member] \| Insurance Group [Member]
Schedule of Equity Method Investments [Line Items]
Reimbursement rate from joint venture partner of Company's surety bond claim losses					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%
Berkadia Commercial Mortgage LLC, Pilot Travel Centers LLC, d/b/a Pilot Flying J, and Electric Transmission Texas, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments, carrying value		$ 3,700,000,000			$ 3,700,000,000		$ 3,500,000,000
Equity method earnings					$ 491,000,000	$ 409,000,000