Accounts Receivable (Details) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts receivable
Gross accounts receivable	$ 1,080	$ 1,241
Allowance for credit losses	(26)	(28)
Net accounts receivable	1,054	1,213
Freight [Member]
Accounts receivable
Gross accounts receivable	869	1,008
Non-freight [Member]
Accounts receivable
Gross accounts receivable	$ 211	$ 233

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
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant