Income taxes - Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Currently payable (receivable)	$ (129)	$ 500
Deferred	56,182	76,457
Other income tax liabilities	554	485
Income taxes, principally deferred	$ 56,607	$ 77,442

Sum of the carrying amounts as of the balance sheet date for a) payments made in advance for income taxes, which will be charged against earnings, b) income taxes previously overpaid to tax authorities representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes, c) the net cumulative amount for all deferred taxes arising from temporary differences between accounting income in accordance with generally accepted accounting principles and tax-basis income, and d) unpaid sum of the known and estimated amounts payable to satisfy all currently due domestic and foreign income tax obligations.

No definition available.

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Namespace Prefix:	brka_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant