Guarantees (Details) - CAD CAD in Millions	Dec. 31, 2017	Dec. 31, 2016
Guarantees [Abstract]
Residual value guarantees on operating lease commitments	CAD 6
Accrued guarantees recorded in accounts payable and accrued liabilities	CAD 9	CAD 5

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsCurrentCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant