Schedule of Assumptions Used in Net Periodic Benefit Cost and Benefit Obligations (Detail)	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Net Periodic Benefit Costs - Discount Rate	3.64%	4.09%	4.12%
Net Periodic Benefit Costs - Expected Return on Plan Assets	4.00%	4.75%	5.50%
Net Periodic Benefit Costs - Rate of Compensation Increase		3.50%	3.50%
Benefit Obligations - Discount Rate	3.33%	3.64%
Benefit Obligations - Rate of Compensation Increase		3.50%