Business segment data - Additional tabular disclosures (Detail) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Segment Reporting Information [Line Items]        
Interest expense   $ 3,853 $ 4,386 $ 3,741
Income tax expense   (321) (21,515) 9,240
Income tax net benefit - Tax Cuts and Jobs Act of 2017 $ (28,200)   (28,200)  
Capital expenditures   14,537 11,708 12,954
Depreciation of tangible assets   7,284 6,968 6,656
Goodwill at year-end 81,258 81,025 81,258 79,486
Total assets 702,095 707,794 702,095 620,854
Operating Businesses [Member]        
Segment Reporting Information [Line Items]        
Interest expense   3,614 4,035 3,409
Income tax expense   5,447 6,030 7,452
Capital expenditures   14,537 11,708 12,954
Depreciation of tangible assets   8,386 7,719 7,411
Goodwill at year-end 81,258 81,025 81,258 79,486
Identifiable assets at year-end 565,423 571,410 565,423 496,824
Operating Businesses [Member] | Insurance Group [Member]        
Segment Reporting Information [Line Items]        
Income tax expense   1,374 (71) 1,585
Capital expenditures   130 170 128
Depreciation of tangible assets   79 84 85
Goodwill at year-end 15,499 15,289 15,499 15,474
Identifiable assets at year-end 294,418 289,746 294,418 234,037
Operating Businesses [Member] | BNSF [Member]        
Segment Reporting Information [Line Items]        
Interest expense   1,041 1,016 992
Income tax expense   1,644 2,369 2,124
Capital expenditures   3,187 3,256 3,819
Depreciation of tangible assets   2,268 2,304 2,079
Goodwill at year-end 14,845 14,851 14,845 14,845
Identifiable assets at year-end 69,438 70,242 69,438 69,277
Operating Businesses [Member] | Berkshire Hathaway Energy [Member]        
Segment Reporting Information [Line Items]        
Interest expense   1,777 2,254 1,715
Income tax expense   (452) 148 371
Capital expenditures   6,241 4,571 5,090
Depreciation of tangible assets   2,830 2,548 2,560
Goodwill at year-end 9,935 9,851 9,935 9,266
Identifiable assets at year-end 77,710 80,543 77,710 74,571
Operating Businesses [Member] | Manufacturing Businesses [Member]        
Segment Reporting Information [Line Items]        
Interest expense   690 679 631
Income tax expense   2,188 2,678 2,442
Capital expenditures   3,116 2,490 2,581
Depreciation of tangible assets   1,890 1,839 1,757
Goodwill at year-end 33,967 34,019 33,967 32,915
Identifiable assets at year-end 97,753 99,912 97,753 93,835
Operating Businesses [Member] | McLane Company [Member]        
Segment Reporting Information [Line Items]        
Interest expense   15 19  
Income tax expense   59 94 169
Capital expenditures   276 289 258
Depreciation of tangible assets   204 193 165
Goodwill at year-end 734 734 734 734
Identifiable assets at year-end 6,090 6,243 6,090 5,896
Operating Businesses [Member] | Service and Retailing Businesses [Member]        
Segment Reporting Information [Line Items]        
Interest expense   91 67 71
Income tax expense   634 812 761
Capital expenditures   1,587 932 1,078
Depreciation of tangible assets   1,115 751 765
Goodwill at year-end 6,278 6,281 6,278 6,252
Identifiable assets at year-end 20,014 24,724 20,014 19,208
Segment Reconciling Items [Member]        
Segment Reporting Information [Line Items]        
Interest expense   458 486 474
Investment and derivative gains/losses, tax   (4,673) 742 1,807
Interest expense, tax   (96) (170) (166)
Equity method investments, tax   (753) 910 396
Income tax net benefit - Tax Cuts and Jobs Act of 2017     (28,200)  
Goodwill at year-end 81,258 81,025 81,258 79,486
Corporate, Eliminations and Other [Member]        
Segment Reporting Information [Line Items]        
Interest expense   (219) (135) (142)
Income tax expense   (246) (827) (249)
Identifiable assets at year-end $ 55,414 $ 55,359 $ 55,414 $ 44,544