New accounting pronouncements - Summary of effects from adopting ASU 2018-12 on affected line items consolidated statement of earnings and comprehensive income (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended						9 Months Ended
		Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Costs and Expenses [Abstract]
Earnings (loss) before income taxes		$ (16,959)			$ (4,258)			$ 73,228	$ (52,609)
Income Tax Expense (Benefit)		(4,392)			(1,560)			13,839	(12,374)
Net earnings (loss)		(12,567)	$ 36,199	$ 35,757	(2,698)	$ (43,242)	$ 5,705	59,389	(40,235)
Net earnings (loss) attributable to Berkshire Hathaway shareholders		(12,767)			(2,798)			58,649	(40,839)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation, pre-tax		(801)			(1,727)			(169)	(3,792)
Long-duration insurance contracts, pre-tax					1,782				7,594
Applicable income taxes					(380)				(1,626)
Other comprehensive income, net		(52)	$ 757	$ 82	(711)	$ 372	$ 2,016	787	1,677
Comprehensive income attributable to Berkshire Hathaway shareholders		$ (12,799)			$ (3,455)			$ 59,429	$ (39,076)
Equivalent Class A [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net earnings (loss) per average equivalent		$ (8,824)			$ (1,907)			$ 40,422	$ (27,768)
Equivalent Class B [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net earnings (loss) per average equivalent	[1]	$ (5.88)			$ (1.27)			$ 26.95	$ (18.51)
Insurance And Other [Member]
Revenues [Abstract]
Insurance premiums earned		$ 21,360			$ 18,754			$ 61,717	$ 54,323
Costs and Expenses [Abstract]
Life, annuity and health insurance benefits		1,144			1,428			3,057	3,951
Insurance underwriting expenses		$ 3,496			2,613			$ 10,812	7,594
Previously Reported [Member]
Costs and Expenses [Abstract]
Earnings (loss) before income taxes					(4,117)				(52,787)
Income Tax Expense (Benefit)					(1,529)				(12,408)
Net earnings (loss)					(2,588)				(40,379)
Net earnings (loss) attributable to Berkshire Hathaway shareholders					(2,688)				(40,983)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation, pre-tax					(1,727)				(3,794)
Other comprehensive income, net					(2,113)				(4,293)
Comprehensive income attributable to Berkshire Hathaway shareholders					$ (4,747)				$ (45,190)
Previously Reported [Member] | Equivalent Class A [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net earnings (loss) per average equivalent					$ (1,832)				$ (27,866)
Previously Reported [Member] | Equivalent Class B [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net earnings (loss) per average equivalent					$ (1.22)				$ (18.58)
Previously Reported [Member] | Insurance And Other [Member]
Revenues [Abstract]
Insurance premiums earned					$ 18,810				$ 54,389
Costs and Expenses [Abstract]
Life, annuity and health insurance benefits					1,450				4,055
Insurance underwriting expenses					2,506				7,734
Revision of Prior Period, Adjustment [Member]
Costs and Expenses [Abstract]
Earnings (loss) before income taxes					(141)				178
Income Tax Expense (Benefit)					(31)				34
Net earnings (loss)					(110)				144
Net earnings (loss) attributable to Berkshire Hathaway shareholders					(110)				144
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation, pre-tax									2
Long-duration insurance contracts, pre-tax					1,782				7,594
Applicable income taxes					(380)				(1,626)
Other comprehensive income, net					1,402				5,970
Comprehensive income attributable to Berkshire Hathaway shareholders					$ 1,292				$ 6,114
Revision of Prior Period, Adjustment [Member] | Equivalent Class A [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net earnings (loss) per average equivalent					$ (75)				$ 98
Revision of Prior Period, Adjustment [Member] | Equivalent Class B [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net earnings (loss) per average equivalent					$ (0.05)				$ 0.07
Revision of Prior Period, Adjustment [Member] | Insurance And Other [Member]
Revenues [Abstract]
Insurance premiums earned					$ (56)				$ (66)
Costs and Expenses [Abstract]
Life, annuity and health insurance benefits					(22)				(104)
Insurance underwriting expenses					$ 107				$ (140)

[1] Net earnings per average equivalent Class B share outstanding are equal to one-fifteen-hundredth of the equivalent Class A amount. See Note 19.