DISPOSITIONS - ASEETS HELD FOR SALE (Details) - Disposal Group, Held-for-sale, Not Discontinued Operations - CAD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accounts receivable and other (current assets held for sale)	$ 363	$ 424
Deferred amounts and other assets (long-term assets held for sale)	1,186	1,190
Accounts payable and other (current liabilities held for sale)	(348)	(315)
Other long-term liabilities (long-term liabilities held for sale)	(43)	(34)
Net assets held for sale	$ 1,158	$ 1,265