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Employee Benefit Plans - Schedule of Assets by Investment Type (Detail) | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
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Chesapeake Pension Plan |  |  |
Asset Category |  |  |
Percentage of assets by investment type | 100.00% | 100.00% | 100.00%
Chesapeake Pension Plan | Investments in equity securities |  |  |
Asset Category |  |  |
Percentage of assets by investment type | 49.02% | 52.70% | 52.93%
Chesapeake Pension Plan | Debt securities |  |  |
Asset Category |  |  |
Percentage of assets by investment type | 40.98% | 37.79% | 37.64%
Chesapeake Pension Plan | Other |  |  |
Asset Category |  |  |
Percentage of assets by investment type | 10.00% | 9.51% | 9.43%
FPU Pension Plan |  |  |
Asset Category |  |  |
Percentage of assets by investment type | 100.00% | 100.00% | 100.00%
FPU Pension Plan | Investments in equity securities |  |  |
Asset Category |  |  |
Percentage of assets by investment type | 50.04% | 55.17% | 53.18%
FPU Pension Plan | Debt securities |  |  |
Asset Category |  |  |
Percentage of assets by investment type | 41.06% | 36.56% | 37.74%
FPU Pension Plan | Other |  |  |
Asset Category |  |  |
Percentage of assets by investment type | 8.90% | 8.27% | 9.08%

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