Pension plans - Defined contribution pension plans - Narrative (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Contribution Plan Disclosure [Line Items]
Contributions to defined contribution plans	$ 737	$ 690	$ 637

Amount of employer contributions to a defined contribution plan.

No definition available.

Name:	brka_DefinedContributionPlanEmployerContributionAmount
Namespace Prefix:	brka_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration