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