SUMMARY OF ACCOUNTING POLICIES - REVENUE RECOGNITION (Details) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Revenue recognized for contracts	CAD 196	CAD 249	CAD 61

Amount of revenue earned from products sold or services provided under the terms of a contract, including, but not limited to, government contracts and construction contracts, classified as other.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Name:	us-gaap_ContractsRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration