Post-employee benefit plans - Defined Benefit Plans Recognized in Comprehensive Income (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Employee Benefits [Abstract]
Cumulative losses recognized directly in equity, January 1	$ (2,984)	$ (2,646)
Actuarial gains (losses) in other comprehensive income	79	(313)
Decrease (increase) in the effect of the asset limit	13	(25)
Cumulative losses recognized directly in equity, December 31	(2,892)	$ (2,984)
Cumulative actuarial losses	3,138
Cumulative decrease in the effect of the asset limit	$ 246

Employee Benefits [Abstract]

No definition available.

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- Definition

Reserve Of Measurements Of Defined Benefit Plans, Actuarial Gains (Loss), Before Tax

+ References

No definition available.

+ Details

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- Definition

Reserve Of Measurements Of Defined Benefit Plans, Before Tax

+ References

No definition available.

+ Details

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- Definition

Reserve Of Measurements Of Defined Benefit Plans, Effect Of Asset Limit, Before Tax

+ References

No definition available.

+ Details

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- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from the gain (loss) on changes in the effect of limiting a net defined benefit asset to the asset ceiling, excluding amounts included in interest income or expense. [Refer: Interest income; Net defined benefit liability (asset); Interest expense (income), net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2018-01-01
-Paragraph 141
-Subparagraph c
-Clause iv
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_141_c_iv&doctype=Standard
-URIDate 2018-03-16

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- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from the remeasurement of that net defined benefit liability (asset). [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2018-01-01
-Paragraph 141
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_141_c&doctype=Standard
-URIDate 2018-03-16

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