Other Long-Term Liabilities - Narrative (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Expected time period for payment of Provision for environmental remediation	10 years
Environmental remediation costs charged to income	$ 6	$ 5	$ 6