SUPPLEMENTAL CASH FLOW INFORMATION - Non-cash Working Capital (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flow Statement [Abstract]
Accounts receivable	$ (70)	$ (11)	$ (520)
Inventory	78	153	(259)
Prepayments and other	(11)	(89)	185
Accounts payable and other	119	(322)	143
Changes in non-cash working capital, net	$ 116	$ (269)	$ (451)

Adjustments For Increase (Decrease), Prepayments And Other

No definition available.

Name:	bbu_AdjustmentsForIncreaseDecreasePrepaymentsAndOther
Namespace Prefix:	bbu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cash Flow Statement [Abstract]

+ References

No definition available.

+ Details

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

- Definition

Adjustments for decrease (increase) in inventories to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Inventories; Profit (loss)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2018-01-01
-Paragraph 20
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2018-03-01&anchor=para_20_a&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_AdjustmentsForDecreaseIncreaseInInventories
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Adjustments for decrease (increase) in trade accounts receivable to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

+ References

+ Details

Name:	ifrs-full_AdjustmentsForDecreaseIncreaseInTradeAccountReceivable
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Adjustments for increase (decrease) in trade and other payables to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Trade and other payables; Profit (loss)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2018-01-01
-Paragraph 20
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2018-03-01&anchor=para_20&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_AdjustmentsForIncreaseDecreaseInTradeAndOtherPayables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) in working capital.

+ References

+ Details

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