General - Narrative (Detail)	6 Months Ended
Oct. 07, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Reduction in premium rate of insurance policies program percentage	15.00%

Reduction in premium rate of insurance policies program percentage.

No definition available.

Name:	brka_ReductionInPremiumRateOfInsurancePoliciesProgramPercentage
Namespace Prefix:	brka_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration