Consolidated statements of comprehensive income (Parenthetical) - CAD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Statement of comprehensive income [abstract]
Actuarial assumption of discount rates	3.70%	3.60%	3.70%	3.60%	3.60%	3.60%	3.80%	4.00%
Income tax relating to cash flow hedges	$ (2)	$ 9	$ (5)	$ 12
Income tax relating to actuarial (losses) gains of defined benefit plans	(136)	95	(94)	214
Income tax relating to changes in fair value of financial liability attributable to change in credit risk of liability of other comprehensive income	$ (6)	$ 0	$ (13)	$ 0

The discount rate used as the significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [member]]

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The amount of income tax relating to amounts recognised in other comprehensive income in relation to cash flow hedges. [Refer: Cash flow hedges [member]; Other comprehensive income]

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The amount of income tax relating to amounts recognised in other comprehensive income in relation to changes in the fair value of financial liabilities attributable to a change in the credit risk of those liabilities. [Refer: Credit risk [member]; Other comprehensive income]

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The amount of income tax relating to amounts recognised in other comprehensive income in relation to remeasurements of defined benefit plans. [Refer: Other comprehensive income; Reserve of remeasurements of defined benefit plans; Defined benefit plans [member]]

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