Business segment data - Additional tabular disclosures (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Segment Reporting Information [Line Items]
Interest expense	$ 4,083		$ 3,961		$ 3,853
Income tax expense	12,440		20,904		(321)
Capital expenditures	13,012		15,979		14,537
Depreciation of tangible assets	8,119		7,566		7,284
Goodwill at year-end	73,734	[1]	81,882	[1]	81,025
Assets	873,729		817,729		707,794
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Interest expense	3,776		3,743		3,614
Income tax expense	4,245		5,336		5,447
Capital expenditures	13,012		15,979		14,537
Depreciation of tangible assets	9,319		8,747		8,386
Goodwill at year-end	73,734		81,882		81,025
Identifiable assets at year-end	719,526		664,703		571,410
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Income tax expense	1,089		1,166		1,374
Capital expenditures	50		108		130
Depreciation of tangible assets	74		82		79
Goodwill at year-end	15,224		15,289		15,289
Identifiable assets at year-end	399,169		364,550		289,746
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Interest expense	1,037		1,070		1,041
Income tax expense	1,631		1,769		1,644
Capital expenditures	3,063		3,608		3,187
Depreciation of tangible assets	2,423		2,350		2,268
Goodwill at year-end	14,851		14,851		14,851
Identifiable assets at year-end	73,809		73,699		70,242
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Interest expense	1,941		1,835		1,777
Income tax expense	(1,010)		(526)		(452)
Capital expenditures	6,765		7,364		6,241
Depreciation of tangible assets	3,376		2,947		2,830
Goodwill at year-end	11,763		9,979		9,851
Identifiable assets at year-end	109,286		88,651		80,543
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Interest expense	737		752		690
Income tax expense	1,795		2,253		2,188
Capital expenditures	2,133		2,981		3,116
Depreciation of tangible assets	2,026		1,951		1,890
Goodwill at year-end	25,512		34,800		34,019
Identifiable assets at year-end	104,318		104,437		99,912
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Interest expense					15
Income tax expense	71		71		59
Capital expenditures	98		158		276
Depreciation of tangible assets	204		225		204
Goodwill at year-end	232		734		734
Identifiable assets at year-end	6,771		6,872		6,243
Operating Businesses [Member] | Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Interest expense	61		86		91
Income tax expense	669		603		634
Capital expenditures	903		1,760		1,587
Depreciation of tangible assets	1,216		1,192		1,115
Goodwill at year-end	6,152		6,229		6,281
Identifiable assets at year-end	26,173		26,494		24,724
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Interest expense	483		416		458
Investment and derivative gains/losses, tax	8,855		15,159		(4,673)
Interest expense, not allocated to segments, tax	(102)		(88)		(96)
Equity method investments, tax	57		148		(753)
Goodwill at year-end	73,734		81,882		81,025
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Interest expense	(176)		(198)		(219)
Income tax expense	(615)		349		(246)
Identifiable assets at year-end	$ 80,469		$ 71,144		$ 55,359

[1] Net of accumulated goodwill impairments of $11.0 billion as of December 31, 2020 and $1.1 billion as of December 31, 2019.