Revenues Contract Liabilities (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Opening balance	$ 2	$ 2
Revenue recognized that was included in the contract liability balance at the beginning of the period	(2)	(2)
Increases due to consideration received, net of revenue recognized during the period	146	2
Closing balance	$ 146	$ 2