Business segment data - Earnings before income taxes (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Investment gains (losses)	$ 20,514	$ (29,778)	$ 46,247	$ 38,041
Non-controlled businesses	222	262	967	1,461
Earnings before income taxes	32,508	(16,959)	86,351	73,228
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	12,949	12,064	38,737	33,048
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	5,628	5,933	19,021	14,045
Investment income	4,594	2,933	11,814	8,230
Operating Businesses [Member] | Insurance Group [Member] | GEICO [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	2,033	1,053	5,747	2,270
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	(689)	510	76	1,050
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	(310)	1,437	1,384	2,495
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	1,846	1,608	4,987	4,872
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	1,101	(147)	1,859	700
Operating Businesses [Member] | Pilot [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	217	291	486	613
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	3,135	3,077	9,178	8,791
Operating Businesses [Member] | McLane [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	145	116	452	358
Operating Businesses [Member] | Service and Retailing [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	877	1,186	2,754	3,669
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Investment gains (losses)	20,514	(29,778)	46,247	38,041
Interest expense, not allocated to segments	(102)	(100)	(317)	(317)
Non-controlled businesses	222	262	967	1,461
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Earnings Before Income Taxes of Operating Businesses	$ (1,075)	$ 593	$ 717	$ 995