INTANGIBLE ASSETS - Cash Generating Units (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Disclosure of information for cash-generating units [line items]
Total	$ 2,997	$ 2,948
Brazilian Regulated Gas Transmission Operation [Member]
Disclosure of information for cash-generating units [line items]
Total	2,949	2,903
U.K. Regulated Distribution Operation [Member]
Disclosure of information for cash-generating units [line items]
Total	$ 48	$ 45

The amount of identifiable non-monetary assets without physical substance. This amount does not include goodwill. [Refer: Goodwill]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2020-01-01
-Paragraph 118
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=38&code=ifrs-tx-2020-en-r&anchor=para_118_e&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 54
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_54_c&doctype=Standard
-URIDate 2020-01-01

Name:	ifrs-full_IntangibleAssetsOtherThanGoodwill
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant