Business segment data - Revenues (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 70,583	$ 63,024	$ 204,296	$ 181,129
BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues	5,761	5,149	16,917	15,101
Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues	7,013	6,226	19,022	15,392
Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	17,456	15,145	50,711	43,176
McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues	12,612	12,040	36,529	35,079
Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	8,654	7,262	25,551	20,221
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	70,656	63,027	204,512	180,918
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income	1,339	1,223	4,212	4,486
Total revenues	19,066	17,136	55,526	51,742
Operating Businesses [Member] | Insurance Group [Member] | GEICO [Member]
Segment Reporting Information [Line Items]
Premiums earned	9,604	8,540	28,073	26,689
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	5,159	4,883	14,868	13,464
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	2,964	2,490	8,373	7,103
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues	5,790	5,176	17,000	15,195
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues	7,013	6,226	19,022	15,392
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	17,496	15,170	50,821	43,238
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues	12,612	12,040	36,529	35,079
Operating Businesses [Member] | Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	8,679	7,279	25,614	20,272
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Total revenues	$ (73)	$ (3)	$ (216)	$ 211