Pensions and Other Benefits - Pension Plan Asset (Detail) - CAD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of fund assets at December 31	$ 12,349	$ 12,808
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at December 31	(11,372)	(11,679)	$ (11,399)
Fair value of fund assets at December 31	12,349	12,808	$ 12,196
Funded Status	977	1,129
Pension plans in deficit [Member] \| Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at December 31	(488)	(505)
Fair value of fund assets at December 31	222	227
Funded Status	(266)	(278)
Pension plans in surplus [Member] \| Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation at December 31	(10,884)	(11,174)
Fair value of fund assets at December 31	12,127	12,581
Funded Status	$ 1,243	$ 1,407

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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