Business segment data - Revenues (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 63,024	$ 64,972	$ 181,129	$ 189,248
BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues	5,149	5,982	15,101	17,558
Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues	6,226	5,720	15,392	15,362
Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	15,145	15,881	43,176	47,130
McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues	12,040	12,604	35,079	37,214
Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	7,262	7,354	20,221	21,798
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	63,027	64,732	180,918	188,725
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income	1,223	1,789	4,486	4,930
Total revenues	17,136	17,112	51,742	49,435
Operating Businesses [Member] | Insurance Group [Member] | GEICO [Member]
Segment Reporting Information [Line Items]
Premiums earned	8,540	8,996	26,689	26,487
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	4,883	3,940	13,464	11,193
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	2,490	2,387	7,103	6,825
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues	5,176	6,021	15,195	17,676
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues	6,226	5,720	15,392	15,362
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	15,170	15,897	43,238	47,173
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues	12,040	12,604	35,079	37,214
Operating Businesses [Member] | Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	7,279	7,378	20,272	21,865
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Total revenues	$ (3)	$ 240	$ 211	$ 523