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Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets (Detail) - CAD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of plan assets |  | $ 8,599 | $ 7,691
Funded Pension Plans [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligation | [1] | 1,042 | 943
Accumulated benefit obligation | [1] | 942 | 852
Fair value of plan assets | [1] | 870 | 739
Accumulated benefit obligation less fair value of plan assets | [1] | 72 | 113
Unfunded Pension Plans [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Projected benefit obligation |  | 597 | 488
Accumulated benefit obligation |  | $ 536 | $ 451
[1] | The amounts shown for funded pension plans with accumulated benefit obligations in excess of plan assets represent the company’s proportionate share of a joint venture sponsored pension plan. For the company sponsored funded plan, plan assets exceeded the accumulated benefit obligation in both 2019 and 2018.

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- Definition Amount of accumulated benefit obligation for defined benefit plan with accumulated benefit obligation in excess of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2417-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2417-114920 + Details
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