SIGNIFICANT ACCOUNTING POLICIES - REGULATION (Details) - CAD ($)	Dec. 31, 2020	Dec. 31, 2019
REGULATION
Regulatory assets	$ 5,629,000,000	$ 5,112,000,000
Deferral for Depreciation for Phase-In Plans under U.S. GAAP Guidance
REGULATION
Regulatory assets	$ 0

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

Name:	us-gaap_RegulatoryAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant