Business segment data - Earnings (loss) before income taxes (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Investment and derivative gains/losses	$ 72,607	$ (22,455)	$ 2,128
Interest expense	(3,961)	(3,853)	(4,386)
Equity method investments	1,176	(2,167)	3,014
Earnings before income taxes	102,696	4,001	23,838
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	29,250	29,156	21,370
Interest expense	(3,743)	(3,614)	(4,035)
Operating Businesses [Member] \| Insurance Group [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	7,017	7,513	1,616
Operating Businesses [Member] \| Insurance Group [Member] \| Insurance Premiums Earned [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	417	2,010	(3,239)
Operating Businesses [Member] \| Insurance Group [Member] \| Interest, Dividend and Other Investment Income [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	6,600	5,503	4,855
Operating Businesses [Member] \| Insurance Group [Member] \| GEICO [Member] \| Insurance Premiums Earned [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	1,506	2,449	(310)
Operating Businesses [Member] \| Insurance Group [Member] \| Berkshire Hathaway Reinsurance Group [Member] \| Insurance Premiums Earned [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	(1,472)	(1,109)	(3,648)
Operating Businesses [Member] \| Insurance Group [Member] \| Berkshire Hathaway Primary Group [Member] \| Insurance Premiums Earned [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	383	670	719
Operating Businesses [Member] \| BNSF [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	7,250	6,863	6,328
Interest expense	(1,070)	(1,041)	(1,016)
Operating Businesses [Member] \| Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	2,618	2,472	2,499
Interest expense	(1,835)	(1,777)	(2,254)
Operating Businesses [Member] \| Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	9,522	9,366	8,324
Interest expense	(752)	(690)	(679)
Operating Businesses [Member] \| McLane Company [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	288	246	299
Interest expense		(15)	(19)
Operating Businesses [Member] \| Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	2,555	2,696	2,304
Interest expense	(86)	(91)	(67)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Investment and derivative gains/losses	72,607	(22,455)	2,128
Interest expense	(416)	(458)	(486)
Equity method investments	1,176	(2,167)	3,014
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	79	(75)	(2,188)
Interest expense	$ 198	$ 219	$ 135

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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