INCOME TAXES - DEFERRED INCOME TAXES (Details) - CAD	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax liabilities
Property, plant and equipment	CAD (4,089,000,000)	CAD (3,867,000,000)
Investments	(6,596,000,000)	(2,938,000,000)
Regulatory assets	(977,000,000)	(439,000,000)
Other	(50,000,000)	(47,000,000)
Total deferred income tax liabilities	(11,712,000,000)	(7,291,000,000)
Deferred income tax assets
Financial instruments	697,000,000	1,215,000,000
Pension and OPEB plans	258,000,000	219,000,000
Loss carryforwards	1,781,000,000	1,189,000,000
Other	1,057,000,000	374,000,000
Total deferred income tax assets	3,793,000,000	2,997,000,000
Less valuation allowance	(286,000,000)	(572,000,000)
Total deferred income tax assets, net	3,507,000,000	2,425,000,000
Net deferred income tax liabilities	(8,205,000,000)	(4,866,000,000)
Total deferred income tax assets	1,090,000,000	1,170,000,000
Total deferred income tax liabilities	(9,295,000,000)	(6,036,000,000)
Deferred taxes on unremitted earnings and currency translation adjustment	0	0
Foreign subsidiaries' undistributed earnings on which deferred income taxes has not been provided	2,100,000,000	4,100,000,000
Canada
Deferred income tax assets
Benefit of unused tax loss carryforwards recognized	3,800,000,000	2,500,000,000
Capital loss carryforwards	143,000,000	0
United States
Deferred income tax assets
Benefit of unused tax loss carryforwards recognized	2,100,000,000	1,300,000,000
Capital loss carryforwards	CAD 20,000,000	CAD 0