Business segment data - Earnings (loss) before income taxes (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Investment and derivative contract gains (losses)	$ (70,275)	$ 20,322
Equity method earnings (losses)	300	168
Earnings (loss) before income taxes	(63,049)	27,647
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	6,846	7,103
Operating Businesses [Member] \| Insurance Group [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	2,109	1,972
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	1,647	1,485
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	984	770
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	(489)	(253)
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	(33)	(30)
Operating Businesses [Member] \| BNSF [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	1,584	1,665
Operating Businesses [Member] \| Berkshire Hathaway Energy [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	419	540
Operating Businesses [Member] \| Manufacturing Businesses [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	2,111	2,194
Operating Businesses [Member] \| McLane Company [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	65	111
Operating Businesses [Member] \| Service and Retailing Businesses [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	558	621
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Investment and derivative contract gains (losses)	(70,275)	20,322
Interest expense, not allocated to segments	(136)	(109)
Equity method earnings (losses)	300	168
Corporate, Eliminations and Other [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes from operating businesses	$ 216	$ 163

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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