Business segment data - Additional tabular disclosures (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Interest expense	$ 3,961	$ 3,853	$ 4,386
Income tax expense	20,904	(321)	(21,515)
Net income tax benefit as a result of enactment of the TCJA			28,200
Capital expenditures	15,979	14,537	11,708
Depreciation of tangible assets	7,566	7,284	6,968
Goodwill at year-end	81,882	81,025	81,258
Assets	817,729	707,794	702,095
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Interest expense	3,743	3,614	4,035
Income tax expense	5,336	5,447	6,030
Capital expenditures	15,979	14,537	11,708
Depreciation of tangible assets	8,747	8,386	7,719
Goodwill at year-end	81,882	81,025	81,258
Identifiable assets at year-end	664,703	571,410	565,423
Operating Businesses [Member] | Insurance Group [Member]
Segment Reporting Information [Line Items]
Income tax expense	1,166	1,374	(71)
Capital expenditures	108	130	170
Depreciation of tangible assets	82	79	84
Goodwill at year-end	15,289	15,289	15,499
Identifiable assets at year-end	364,550	289,746	294,418
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Interest expense	1,070	1,041	1,016
Income tax expense	1,769	1,644	2,369
Capital expenditures	3,608	3,187	3,256
Depreciation of tangible assets	2,350	2,268	2,304
Goodwill at year-end	14,851	14,851	14,845
Identifiable assets at year-end	73,699	70,242	69,438
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Interest expense	1,835	1,777	2,254
Income tax expense	(526)	(452)	148
Capital expenditures	7,364	6,241	4,571
Depreciation of tangible assets	2,947	2,830	2,548
Goodwill at year-end	9,979	9,851	9,935
Identifiable assets at year-end	88,651	80,543	77,710
Operating Businesses [Member] | Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Interest expense	752	690	679
Income tax expense	2,253	2,188	2,678
Capital expenditures	2,981	3,116	2,490
Depreciation of tangible assets	1,951	1,890	1,839
Goodwill at year-end	34,800	34,019	33,967
Identifiable assets at year-end	104,437	99,912	97,753
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Interest expense		15	19
Income tax expense	71	59	94
Capital expenditures	158	276	289
Depreciation of tangible assets	225	204	193
Goodwill at year-end	734	734	734
Identifiable assets at year-end	6,872	6,243	6,090
Operating Businesses [Member] | Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Interest expense	86	91	67
Income tax expense	603	634	812
Capital expenditures	1,760	1,587	932
Depreciation of tangible assets	1,192	1,115	751
Goodwill at year-end	6,229	6,281	6,278
Identifiable assets at year-end	26,494	24,724	20,014
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Interest expense	416	458	486
Investment and derivative gains/losses, tax	15,159	(4,673)	742
Interest expense, not allocated to segments, tax	(88)	(96)	(170)
Equity method investments, tax	148	(753)	910
Net income tax benefit as a result of enactment of the TCJA			(28,200)
Goodwill at year-end	81,882	81,025	81,258
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Interest expense	(198)	(219)	(135)
Income tax expense	349	(246)	(827)
Identifiable assets at year-end	$ 71,144	$ 55,359	$ 55,414