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Weighted Asset Allocations by Asset Category (Detail) | Dec. 31, 2017 | Dec. 31, 2016
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Pension And Other Post-Retirement Benefits |  |
Average Assets Allocation | 100.00% | 100.00%
Equity Securities |  |
Pension And Other Post-Retirement Benefits |  |
Average Assets Allocation | 45.00% | 48.00%
Debt Securities |  |
Pension And Other Post-Retirement Benefits |  |
Average Assets Allocation | 43.00% | 37.00%
Real estate |  |
Pension And Other Post-Retirement Benefits |  |
Average Assets Allocation | 9.00% | 10.00%
Private equity |  |
Pension And Other Post-Retirement Benefits |  |
Average Assets Allocation | 2.00% | 4.00%
Other |  |
Pension And Other Post-Retirement Benefits |  |
Average Assets Allocation | 1.00% | 1.00%

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