Business segment data - Revenues (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 65,368	$ 64,972	$ 63,598	$ 60,678	$ 63,714	$ 63,450	$ 62,200	$ 58,473	$ 254,616	$ 247,837	$ 239,933
BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues									23,357	23,703
Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues									20,096	19,970
Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									62,624	61,770
McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues									50,458	49,987
Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									29,399	28,849
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									253,997	247,587	240,342
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned									61,078	57,418	60,597
Interest, dividend and other investment income									6,615	5,518	4,865
Total revenues									67,693	62,936	65,462
Operating Businesses [Member] | Insurance Group [Member] | GEICO [Member]
Segment Reporting Information [Line Items]
Premiums earned									35,572	33,363	29,441
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned									16,341	15,944	24,013
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned									9,165	8,111	7,143
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues									23,515	23,855	21,387
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues									20,114	19,987	18,854
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									62,730	61,883	57,645
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues									50,458	49,987	49,775
Operating Businesses [Member] | Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues									29,487	28,939	27,219
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Total revenues									$ 619	$ 250	$ (409)