Other Long-Term Liabilities - Narrative (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Expected time period for payment of provision for environmental remediation	P10Y
Environmental remediation costs charged to income	$ 6	$ 6	$ 5