Consolidated Statements of Earnings (Parenthetical)	12 Months Ended
Dec. 31, 2017
Class B [Member]
Ratio of earnings per Class B share to earnings per Class A share	0.000667

Ratio representing the net earnings per equivalent common share and dividend and distribution rights of Class B shares to Class A shares.

No definition available.

Name:	brka_DistributionRightsComparedToClassACommonShares
Namespace Prefix:	brka_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration