Condensed Financial Information - Statements of Earnings and Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
From consolidated subsidiaries:
Investment gains (losses)																	$ 71,123	$ (22,155)	$ 1,410
Equity method earnings (losses)																	1,176	(2,167)	3,014
Total revenues	$ 65,368		$ 64,972		$ 63,598		$ 60,678		$ 63,714		$ 63,450		$ 62,200		$ 58,473		254,616	247,837	239,933
Cost and expense items:
Interest expense																	3,961	3,853	4,386
Income tax expense (benefit)																	20,904	(321)	(21,515)
Total costs and expenses																	225,703	219,214	221,237
Net earnings attributable to Berkshire Hathaway shareholders	$ 29,159	[1]	$ 16,524	[1]	$ 14,073	[1]	$ 21,661	[1]	$ (25,392)	[1]	$ 18,540	[1]	$ 12,011	[1]	$ (1,138)	[1]	81,417	4,021	44,940
Comprehensive income attributable to Berkshire Hathaway shareholders																	81,189	1,810	66,213
Berkshire Hathaway Inc. (Parent) [Member]
From consolidated subsidiaries:
Dividends and distributions																	15,603	9,658	5,367
Undistributed earnings (losses)																	65,237	(3,952)	37,832
Total income from consolidated subsidiaries																	80,840	5,706	43,199
Investment gains (losses)																	(125)	(4)	(1)
Equity method earnings (losses)																	493	(2,730)	2,938
Other income																	780	649	350
Total revenues																	81,988	3,621	46,486
Cost and expense items:
General and administrative																	122	216	159
Interest expense																	591	601	522
Foreign exchange (gains) losses on non-U.S. Dollar denominated debt																	(193)	(366)	1,008
Income tax expense (benefit)																	51	(851)	(143)
Total costs and expenses																	571	(400)	1,546
Net earnings attributable to Berkshire Hathaway shareholders																	81,417	4,021	44,940
Other comprehensive income attributable to Berkshire Hathaway shareholders																	(228)	(2,211)	21,273
Comprehensive income attributable to Berkshire Hathaway shareholders																	$ 81,189	$ 1,810	$ 66,213

[1] * Includes after-tax investment and derivative gains/losses as follows:       1^st Quarter     2^nd Quarter     3^rd Quarter     4^th Quarter   2019   $ 16,106     $ 7,934     $ 8,666     $ 24,739   2018     (6,426 )     5,118       11,660       (28,089 )