Business segment data - Revenues by segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 62,200	$ 57,256	$ 120,673	$ 121,626
BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues			11,435
Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues			9,562
Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues			26,752
McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues			24,616
Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues			13,597
Finance and Financial Products Reportable Segment [Member]
Segment Reporting Information [Line Items]
Total revenues			4,426
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	62,184	57,389	120,679	121,830
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income	1,399	1,284	2,612	2,416
Total revenues	15,548	13,651	30,134	36,536
Operating Businesses [Member] | Insurance Group [Member] | GEICO [Member]
Segment Reporting Information [Line Items]
Premiums earned	8,284	7,244	16,199	14,089
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	3,912	3,364	7,452	16,596
Operating Businesses [Member] | Insurance Group [Member] | Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	1,953	1,759	3,871	3,435
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Total revenues	5,878	5,250	11,502	10,435
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Total revenues	5,050	4,602	9,562	8,833
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	13,853	12,738	26,787	24,835
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Total revenues	12,427	12,581	24,616	24,682
Operating Businesses [Member] | Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Total revenues	7,062	6,550	13,649	12,643
Operating Businesses [Member] | Finance and Financial Products Reportable Segment [Member]
Segment Reporting Information [Line Items]
Total revenues	2,366	2,017	4,429	3,866
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Total revenues	$ 16	$ (133)	$ (6)	$ (204)