Accounts Receivable (Details) - CAD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable
Gross accounts receivable	$ 1,241	$ 1,195
Allowance for doubtful accounts	(28)	(26)
Net accounts receivable	1,213	1,169
Freight [Member]
Accounts receivable
Gross accounts receivable	1,008	974
Non-freight [Member]
Accounts receivable
Gross accounts receivable	$ 233	$ 221

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant