Revenue Recognition Contract Balances (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Change in Contract with Customer, Asset [Abstract]
Balance at January 1, 2018	$ 2.1
Additions	17.9
Transfer to Accounts receivable	(18.4)
Balance at December 31, 2018	1.6
Change in Contract with Customer, Liability [Abstract]
Balance at January 1, 2018	68.2
Additions	154.5
Transfer to Revenues	(143.1)
Other	0.7
Balance at December 31, 2018	80.3
Contract liabilities, current	12.8	$ 14.7
Contract with Customer, Liability, Noncurrent	$ 67.5