Schedule II - Valuation and Qualifying Accounts (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accruals for personal injury and other claims provision
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance at January 1	$ 152	$ 118	$ 130
Additions charged to expenses	142	93	66
Payments and other reductions	(152)	(60)	(77)
Impact of FX	(1)	1	(1)
Ending balance at December 31	141	152	118
Environmental liabilities
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance at January 1	82	78	85
Additions charged to expenses	6	6	5
Payments and other reductions	(8)	(7)	(8)
Impact of FX	(3)	5	(4)
Ending balance at December 31	$ 77	$ 82	$ 78