INSURANCE CONTRACTS - Movement in Unearned Premium Reserve (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($)
Insurance Contracts [Abstract]
Unearned premium reserves, beginning of year	$ 0
Acquisitions through business combinations	1,603
Premiums written during the year	26
Premiums earned during the year	(28)
Foreign currency translation	24
Unearned premium reserves, end of year	$ 1,625

Acquisitions Through Business Combinations, Unearned Premiums

No definition available.

Name:	bbu_AcquisitionsThroughBusinessCombinationsUnearnedPremiums
Namespace Prefix:	bbu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Increase (Decrease) Through Net Exchange Differences, Unearned Premiums

+ References

No definition available.

+ Details

Name:	bbu_IncreaseDecreaseThroughNetExchangeDifferencesUnearnedPremiums
Namespace Prefix:	bbu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Insurance Contracts [Abstract]

+ References

No definition available.

+ Details

Name:	bbu_InsuranceContractsAbstract
Namespace Prefix:	bbu_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of premiums earned on insurance contracts net of reinsurance premiums. [Refer: Types of insurance contracts [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 85
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_85&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_NetEarnedPremium
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of premiums written, net of amounts reinsured with third parties.

+ References

+ Details

Name:	ifrs-full_PremiumsWrittenNetOfReinsurance
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of liability for written premiums on insurance contracts that have not yet been earned. [Refer: Types of insurance contracts [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Note Expiry date 2021-01-01
-Name IFRS
-Number 4
-IssueDate 2018-01-01
-Paragraph IG22
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=4&date=2018-03-02&anchor=para_IG22_a&doctype=Implementation%20Guidance&book=b
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Note Expiry date 2021-01-01
-Name IFRS
-Number 4
-IssueDate 2018-01-01
-Paragraph 37
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=4&date=2018-03-02&anchor=para_37_b&doctype=Standard&book=b
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_UnearnedPremiums
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant