INCOME TAXES - DEFERRED INCOME TAXES (Details) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred income tax liabilities
Property, plant and equipment	$ (7,786)	$ (7,290)
Investments	(4,649)	(4,620)
Regulatory assets	(1,156)	(1,052)
Other	(127)	(40)
Total deferred income tax liabilities	(13,718)	(13,002)
Deferred income tax assets
Financial instruments	518	679
Pension and OPEB plans	251	206
Loss carryforwards	2,005	1,693
Other	1,461	1,641
Total deferred income tax assets	4,235	4,219
Less valuation allowance	(79)	(84)
Total deferred income tax assets, net	4,156	4,135
Net deferred income tax liabilities	(9,562)	(8,867)
Deferred income taxes	770	1,000
Total deferred income tax liabilities	(10,332)	(9,867)
Foreign subsidiaries' undistributed earnings on which deferred income taxes has not been provided	5,500	5,300
Canada
Deferred income tax assets
Benefit of unused tax loss carryforwards recognized	2,600	3,200
US
Deferred income tax assets
Benefit of unused tax loss carryforwards recognized	$ 5,800	$ 3,600