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Change in Plan Assets and Plan Assets in Excess of Less Than Projected Benefit Obligation (Detail) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Schedule Of Defined Benefit Plans Disclosures [Line Items] |  |  |
Fair value at January 1 |  | $ 7,691 |
Fair value at December 31 |  | 8,599 | $ 7,691
Pension benefits |  |  |
Schedule Of Defined Benefit Plans Disclosures [Line Items] |  |  |
Fair value at January 1 |  | 7,691 | 7,870
Actual return (loss) on plan assets |  | 1,114 | 20
Company contributions |  | 211 | 203
Benefits paid | [1] | (417) | (402)
Fair value at December 31 |  | 8,599 | 7,691
Funded plans |  | (590) | (180)
Unfunded plans |  | (597) | (488)
Total | [2] | (1,187) | (668)
Other postretirement benefits |  |  |
Schedule Of Defined Benefit Plans Disclosures [Line Items] |  |  |
Unfunded plans |  | (693) | (582)
Total | [2] | $ (693) | $ (582)
[1] | Benefit payments for funded plans only.
[2] | Fair value of assets less projected benefit obligation shown above.

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