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Schedule of Fair Values of Defined Benefit Plans Determined Using Fair Value Hierarchy of Inputs (Detail) - USD ($)
$ in Thousands
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans $ 39,009 $ 36,541 $ 33,412
Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 853 144  
Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 38,156 36,397  
Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 3,470 4,525  
Equity Securities [Member] | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 3,470 4,525  
Fixed Income Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 34,579 31,516  
Fixed Income Securities [Member] | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 34,579 31,516  
Real Estate Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 107 144  
Real Estate Funds [Member] | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 107 144  
Cash Equivalents [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans 853 144  
Cash Equivalents [Member] | Fair Value, Inputs, Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans $ 853 144  
Commodity Linked Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans   212  
Commodity Linked Funds [Member] | Fair Value, Inputs, Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair values of defined benefit plans   $ 212