Condensed Financial Information - Statements of Earnings and Comprehensive Income (Detail) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
From consolidated subsidiaries:                      
Investment gains (losses)                 $ (22,155) $ 1,410 $ 7,553
Equity method earnings (losses)                 (2,167) 3,014 1,109
Total revenues $ 63,714 $ 63,450 $ 62,200 $ 58,473 $ 58,800 $ 59,507 $ 57,256 $ 64,370 247,837 239,933 215,114
Cost and expense items:                      
Interest expense                 3,853 4,386 3,741
Income tax expense (benefit)                 (321) (21,515) 9,240
Total costs and expenses                 219,214 221,237 190,860
Net earnings attributable to Berkshire Hathaway shareholders $ (25,392) [1] $ 18,540 [1] $ 12,011 [1] $ (1,138) [1] $ 32,551 [1] $ 4,067 [1] $ 4,262 [1] $ 4,060 [1] 4,021 44,940 24,074
Comprehensive income attributable to Berkshire Hathaway shareholders                 1,810 66,213 27,390
Berkshire Hathaway Inc. (Parent) [Member]                      
From consolidated subsidiaries:                      
Dividends                 9,658 5,367 9,862
Undistributed earnings (losses)                 (3,952) 37,832 13,264
Total income from consolidated subsidiaries                 5,706 43,199 23,126
Investment gains (losses)                 (4) (1) 700
Equity method earnings (losses)                 (2,730) 2,938 923
Other income                 649 350 262
Total revenues                 3,621 46,486 25,011
Cost and expense items:                      
General and administrative                 216 159 80
Interest expense                 601 522 452
Foreign exchange (gains) losses Euro-denominated senior notes                 (366) 1,008 (244)
Income tax expense (benefit)                 (851) (143) 649
Total costs and expenses                 (400) 1,546 937
Net earnings attributable to Berkshire Hathaway shareholders                 4,021 44,940 24,074
Other comprehensive income attributable to Berkshire Hathaway shareholders                 (2,211) 21,273 3,316
Comprehensive income attributable to Berkshire Hathaway shareholders                 $ 1,810 $ 66,213 $ 27,390
[1] Includes after-tax investment and derivative gains/losses and a one-time income tax net benefit attributable to the enactment of the Tax Cuts and Jobs Act of 2017 as follows: 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Investment and derivative gains/losses - 2018 $ (6,426) $ 5,118 $ 11,660 $ (28,089) Investment and derivative gains/losses - 2017 504 143 623 107 Income tax net benefit - Tax Cuts and Jobs Act of 2017 - - - 28,200