Consolidated Statements of Earnings (Parenthetical)	9 Months Ended
Sep. 30, 2018
Class B [Member]
Economic equivalent of Class B share to Class A share	0.0667%

Economic equivalent of Class B share represented as a fraction of Class A share.

No definition available.

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