Represents the quantification of the effect of adopting the new accounting standard or change in accounting principle expected by the entity to have a significant effect on the entity's financial statements.

No definition available.

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

Accounting Changes - Narrative (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Standards Update 2017-07 [Member]
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement, Effect of Adoption, Quantification		$ 274	$ 167
Accounting Standards Update 2016-02 [Member]
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement, Effect of Adoption, Quantification	$ 400