Business segment data - Revenues (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total revenues	$ 64,381	$ 63,024	$ 56,840	$ 61,265	$ 65,368	$ 64,972	$ 63,598	$ 60,678	$ 245,510	$ 254,616	$ 247,837
BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues									20,750	23,357	23,703
Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues									21,014	20,096	19,970
Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									58,978	62,624	61,770
McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues									46,840	50,458	49,987
Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									28,111	29,399	28,849
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									245,358	253,997	247,587
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned									63,401	61,078	57,418
Interest, dividend and other investment income									5,960	6,615	5,518
Total revenues									69,361	67,693	62,936
Operating Businesses [Member] | Insurance Group [Member] | GEICO [Member]
Segment Reporting Information [Line Items]
Premiums earned									35,093	35,572	33,363
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned									18,693	16,341	15,944
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned									9,615	9,165	8,111
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues									20,869	23,515	23,855
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues									21,031	20,114	19,987
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									59,079	62,730	61,883
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues									46,840	50,458	49,987
Operating Businesses [Member] | Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									28,178	29,487	28,939
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Total revenues									$ 152	$ 619	$ 250