Condensed Financial Information - Statements of Earnings and Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
From consolidated subsidiaries:
Equity in net earnings of The Kraft Heinz Company																	$ 2,938	$ 923	$ (122)
Total revenues	$ 58,907		$ 60,525		$ 57,518		$ 65,187		$ 58,344		$ 58,843		$ 54,254		$ 52,163		242,137	223,604	210,943
Cost and expense items:
Interest expense																	5,394	3,497	3,515
Income taxes																	(21,515)	9,240	10,532
Total costs and expenses																	221,237	190,860	175,875
Net earnings attributable to Berkshire Hathaway shareholders	$ 32,551	[1]	$ 4,067	[1]	$ 4,262	[1]	$ 4,060	[1]	$ 6,286	[1]	$ 7,198	[1]	$ 5,001	[1]	$ 5,589	[1]	44,940	24,074	24,083
Comprehensive income attributable to Berkshire Hathaway shareholders																	66,213	27,390	15,333
Berkshire Hathaway Inc. (Parent) [Member]
From consolidated subsidiaries:
Dividends																	5,367	9,862	10,519
Undistributed earnings																	37,832	13,264	8,508
Total income from consolidated subsidiaries																	43,199	23,126	19,027
Investment gains/losses																	(1)	700	16
Investment holding gain in The Kraft Heinz Company																			6,838
Equity in net earnings of The Kraft Heinz Company																	2,938	923	(122)
Other income																	350	262	963
Total revenues																	46,486	25,011	26,722
Cost and expense items:
General and administrative																	159	80	73
Interest expense																	1,530	208	302
Income taxes																	(143)	649	2,264
Total costs and expenses																	1,546	937	2,639
Net earnings attributable to Berkshire Hathaway shareholders																	44,940	24,074	24,083
Other comprehensive income attributable to Berkshire Hathaway shareholders																	21,273	3,316	(8,750)
Comprehensive income attributable to Berkshire Hathaway shareholders																	$ 66,213	$ 27,390	$ 15,333

[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 - 2017 $ 504 $ 143 $ 623 $ 107 Investment and derivative gains/losses - 2016 1,852 394 2,347 1,904 Income tax net benefit - Tax Cuts and Jobs Act of 2017 - - - 28,200