Business segment data - Revenues (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 64,599	$ 61,265
BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues	5,378	5,380
Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues	5,924	4,507
Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	15,880	15,014
McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues	11,622	11,821
Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	7,943	6,938
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	64,656	61,132
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income	1,414	1,648
Total revenues	17,838	17,396
Operating Businesses [Member] | Insurance Group [Member] | GEICO [Member]
Segment Reporting Information [Line Items]
Premiums earned	8,923	9,109
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	4,847	4,270
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	2,654	2,369
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues	5,401	5,417
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues	5,924	4,507
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	15,913	15,035
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues	11,622	11,821
Operating Businesses [Member] | Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	7,958	6,956
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Total revenues	$ (57)	$ 133