Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Weighted Average Actuarial Assumptions Used to Develop Projected Benefit Obligation (Detail)

v3.21.1
Employee Benefit Plans - Weighted Average Actuarial Assumptions Used to Develop Projected Benefit Obligation (Detail) - Other Postretirement Benefit Plans [Member]
Mar. 31, 2021
Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]    
Discount rate 2.34% 3.01%
Medical care cost trend rate 7.00% 7.00%