Interest Expense, net (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest Income (Expense), Net [Abstract]
Interest expense on KMI Loans	$ 0.0	$ 10.0	$ 21.3
Interest expense on credit facilities	2.1	0.9	0.0
Amortization expense of debt issuance costs	0.6	0.5	0.0
Interest expense, other	0.4	0.4	0.0
Interest income	(29.7)	0.0	0.0
Capitalized debt financing costs	(0.6)	(3.6)	(2.8)
Interest Income (Expense), Net, Total	$ (27.2)	$ 8.2	$ 18.5