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Notes payable and other borrowings - Narrative (Detail) € in Millions, £ in Millions, $ in Millions, ¥ in Billions	1 Months Ended					3 Months Ended		9 Months Ended
	Jul. 31, 2025 USD ($)	Jul. 31, 2025 JPY (¥)	Jun. 30, 2025 USD ($)	Apr. 30, 2025 USD ($)	Apr. 30, 2025 JPY (¥)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 JPY (¥)	Sep. 30, 2025 EUR (€)	Sep. 30, 2025 GBP (£)	Dec. 31, 2024 USD ($)
Berkshire Hathaway Inc. (Parent) [Member] \| Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Notes payable and other borrowings										¥ 2,188.0	€ 4,850	£ 1,750
Line of Credit and Commercial Paper Facilities [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Unused and available lines of credit						$ 10,900		$ 10,900
Line of Credit and Commercial Paper Facilities [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy and Subsidiaries [Member]
Debt Instrument [Line Items]
Unused and available lines of credit						9,900		9,900
Insurance and Other [Member]
Debt Instrument [Line Items]
Notes payable and other borrowings						45,617		45,617					$ 44,885
Insurance and Other [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Subsidiaries Excluding Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Guarantee obligation						1,700		1,700
Insurance and Other [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Short-term borrowings						$ 1,320		$ 1,320					1,315
Weighted average interest rate, percentage						5.10%		5.10%		5.10%	5.10%	5.10%
Notes payable and other borrowings						$ 3,544		$ 3,544					4,564
Insurance and Other [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Repayments of borrowings								1,600
Insurance and Other [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Gains (loss) attributable to changes in foreign currency exchange rates						433	$ (1,500)	$ (1,700)	$ (136)
Insurance and Other [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Debt Due 2028 to 2055 [Member]
Debt Instrument [Line Items]
Principal amount of debt issued				$ 632	¥ 90.0
Interest rate during period				1.60%	1.60%
Insurance and Other [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Debt Due 2030 to 2040 [Member]
Debt Instrument [Line Items]
Principal amount of debt issued	$ 1,000	¥ 151.5
Interest rate during period	2.30%	2.30%
Insurance and Other [Member] \| Minimum [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Debt maturity year								2025
Insurance and Other [Member] \| Minimum [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Debt Due 2028 to 2055 [Member]
Debt Instrument [Line Items]
Debt maturity year				2028	2028
Insurance and Other [Member] \| Minimum [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Debt Due 2030 to 2040 [Member]
Debt Instrument [Line Items]
Debt maturity year	2030	2030
Insurance and Other [Member] \| Maximum [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Debt maturity year								2051
Insurance and Other [Member] \| Maximum [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Debt Due 2028 to 2055 [Member]
Debt Instrument [Line Items]
Debt maturity year				2055	2055
Insurance and Other [Member] \| Maximum [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Debt Due 2030 to 2040 [Member]
Debt Instrument [Line Items]
Debt maturity year	2040	2040
Railroad, Utilities and Energy [Member]
Debt Instrument [Line Items]
Notes payable and other borrowings						81,626		$ 81,626					79,877
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy and Subsidiaries [Member]
Debt Instrument [Line Items]
Short-term borrowings						$ 1,719		$ 1,719					1,123
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy Subsidiaries [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage						4.80%		4.80%		4.80%	4.80%	4.80%
Notes payable and other borrowings						$ 44,943		$ 44,943					$ 42,150
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Term Debt [Member] \| Berkshire Hathaway Energy Subsidiaries [Member]
Debt Instrument [Line Items]
Repayments of borrowings								2,400
Short-term borrowings						$ 600		600
Principal amount of debt issued								$ 3,100
Weighted average interest rate, percentage						6.40%		6.40%		6.40%	6.40%	6.40%
Railroad, Utilities and Energy [Member] \| Senior Unsecured Debentures [Member] \| Subsidiaries [Member] \| BNSF [Member]
Debt Instrument [Line Items]
Repayments of borrowings								$ 900
Principal amount of debt issued			$ 900
Debt instrument, interest rate, stated percentage			5.80%
Debt maturity year			2056
Railroad, Utilities and Energy [Member] \| Minimum [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy Subsidiaries [Member]
Debt Instrument [Line Items]
Debt maturity year								2025
Railroad, Utilities and Energy [Member] \| Minimum [Member] \| Subsidiaries [Member] \| Term Debt [Member] \| Berkshire Hathaway Energy Subsidiaries [Member]
Debt Instrument [Line Items]
Debt maturity year								2035
Railroad, Utilities and Energy [Member] \| Maximum [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy Subsidiaries [Member]
Debt Instrument [Line Items]
Debt maturity year								2064
Railroad, Utilities and Energy [Member] \| Maximum [Member] \| Subsidiaries [Member] \| Term Debt [Member] \| Berkshire Hathaway Energy Subsidiaries [Member]
Debt Instrument [Line Items]
Debt maturity year								2055