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Employee Benefit Plans - Narrative (Details) - USD ($)
12 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2018
Retirement Benefits [Abstract]        
Employer matching contribution, percentage of match 6.00%      
Employees’ capital accumulation plan, total expense recognized $ 166,300,000 $ 151,000,000.0 $ 136,300,000  
Employees’ capital accumulation plan, company-paid contributions 163,000,000.0 146,500,000 130,900,000  
Defined Benefit Plan Disclosure [Line Items]        
Unrecognized gross actuarial gain 3,400,000 6,600,000    
Unrecognized actuarial gain, tax 900,000 1,700,000    
Long-term disability obligation $ 10,900,000 10,700,000    
Reduction to plan liability     $ 11,200,000  
Deferred compensation plans, maximum eligible deferral of compensation percentage 100.00%      
Long-term deferred compensation costs $ 14,100,000 5,900,000    
Retired Officers' Bonus Plan        
Defined Benefit Plan Disclosure [Line Items]        
Deferred compensation arrangement with individual, annual cash award granted per year of service, amount 10,000      
Other Postretirement Benefits Plan | Officer        
Defined Benefit Plan Disclosure [Line Items]        
Benefit obligation 3,400,000 3,800,000    
Retired Officers' Bonus Plan and Retired Vice-President Bonus Plan | Other Postretirement Benefits Plan        
Defined Benefit Plan Disclosure [Line Items]        
Defined benefit plan, funded (unfunded) status of plan (4,500,000) (4,800,000)    
Fair value of plan assets $ 0 $ 0    
Retired Officers' Bonus Plan | Other Postretirement Benefits Plan        
Defined Benefit Plan Disclosure [Line Items]        
Weighted-average discount rate for benefit obligation (as a percent) 3.40% 3.60% 4.10%  
Retired Officers' Bonus Plan | Other Postretirement Benefits Plan | Officer        
Defined Benefit Plan Disclosure [Line Items]        
Total pension expense $ 600,000 $ 600,000 $ 700,000  
Benefits paid $ 1,100,000 $ 600,000 $ 800,000  
Retired Vice Presidents' Bonus Plan | Other Postretirement Benefits Plan        
Defined Benefit Plan Disclosure [Line Items]        
Weighted-average discount rate for benefit obligation (as a percent) 3.40% 3.60% 4.10%  
Benefits paid $ 0 $ 100,000 $ 0  
Benefit obligation 1,100,000 1,000,000.0    
Retired Vice Presidents' Bonus Plan | Other Postretirement Benefits Plan | Officer        
Defined Benefit Plan Disclosure [Line Items]        
Total pension expense $ 200,000 $ 200,000 $ 200,000  
Officer Medical Plan | Other Postretirement Benefits Plan        
Defined Benefit Plan Disclosure [Line Items]        
Weighted-average discount rate for benefit obligation (as a percent) 3.40% 3.60% 4.10%  
Defined benefit plan, funded (unfunded) status of plan $ (121,500,000) $ (119,600,000)    
Total pension expense 9,894,000 9,814,000 $ 13,190,000  
Benefits paid 4,519,000 3,785,000 3,742,000  
Benefit obligation 121,518,000 119,609,000 120,341,000 $ 126,886,000
Fair value of plan assets $ 0 $ 0 $ 0 $ 0