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Weighted-Average Asset Allocation of Said Plan Assets for Pension Benefits (Detail) - Pension
Mar. 31, 2020
Funds managed by trust  
Weighted-average asset allocation 100.00%
Government Securities  
Funds managed by trust  
Weighted-average asset allocation 20.80%
Debenture and bonds  
Funds managed by trust  
Weighted-average asset allocation 17.10%
Other  
Funds managed by trust  
Weighted-average asset allocation 62.10%