Goodwill and Intangible Assets (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill
Goodwill, Opening balance	$ 178	$ 191
Amortization	0	0
Foreign exchange impact	16	(13)
Goodwill, Ending balance	194	178
Intangible assets
Cost, Opening balance	22	22
Accumulated amortization, Opening balance	(13)	(11)
Net carrying amount, Opening balance	9	11
Amortization	(1)	(1)
Foreign exchange impact	0	(1)
Cost, Ending Balance	22	22
Accumulated amortization, Ending Balance	(14)	(13)
Net carrying amount, Ending balance	8	9
Total goodwill and intangible assets
Opening Balance	187	202
Amortization	(1)	(1)
Foreign exchange impact	16	(14)
Ending Balance	$ 202	$ 187