Business segment data - Earnings before income taxes (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Investment and derivative gains/losses	$ (22,455)	$ 2,128	$ 8,304
Interest expense	(3,853)	(4,386)	(3,741)
Equity method investments	(2,167)	3,014	1,109
Earnings before income taxes	4,001	23,838	33,667
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	29,156	21,370	25,408
Interest expense	(3,614)	(4,035)	(3,409)
Operating Businesses [Member] \| Insurance Group [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	7,513	1,616	6,613
Operating Businesses [Member] \| Insurance Group [Member] \| Insurance Premiums Earned [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	2,010	(3,239)	2,131
Operating Businesses [Member] \| Insurance Group [Member] \| Interest, Dividend and Other Investment Income [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	5,503	4,855	4,482
Operating Businesses [Member] \| Insurance Group [Member] \| GEICO [Member] \| Insurance Premiums Earned [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	2,449	(310)	462
Operating Businesses [Member] \| Insurance Group [Member] \| Berkshire Hathaway Reinsurance Group [Member] \| Insurance Premiums Earned [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	(1,109)	(3,648)	1,012
Operating Businesses [Member] \| Insurance Group [Member] \| Berkshire Hathaway Primary Group [Member] \| Insurance Premiums Earned [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	670	719	657
Operating Businesses [Member] \| BNSF [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	6,863	6,328	5,693
Interest expense	(1,041)	(1,016)	(992)
Operating Businesses [Member] \| Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	2,472	2,499	2,878
Interest expense	(1,777)	(2,254)	(1,715)
Operating Businesses [Member] \| Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	9,366	8,324	7,735
Interest expense	(690)	(679)	(631)
Operating Businesses [Member] \| McLane Company [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	246	299	431
Interest expense	(15)	(19)
Operating Businesses [Member] \| Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	2,696	2,304	2,058
Interest expense	(91)	(67)	(71)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Investment and derivative gains/losses	(22,455)	2,128	8,304
Interest expense	(458)	(486)	(474)
Equity method investments	(2,167)	3,014	1,109
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes from operating businesses	(75)	(2,188)	(680)
Interest expense	$ 219	$ 135	$ 142

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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