INSURANCE CONTRACTS - Narrative (Details)	12 Months Ended
Dec. 31, 2019
Insurance Contracts [Abstract]
Premiums written recognised as premiums earned in the first five years, percentage	80.00%

Premiums Written Recognised As Premiums Earned Within Five Years, Percentage

No definition available.

Name:	bbu_PremiumsWrittenRecognisedAsPremiumsEarnedWithinFiveYearsPercentage
Namespace Prefix:	bbu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration