Pension and Other Benefit Plans - Schedule of Weighted-Average Rates Used to Determine Net Periodic Pension Cost (Details)	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.70%	4.10%
Expected long-term rate of return on assets	7.40%	7.80%
Retiree Medical Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.50%	4.00%
Expected long-term rate of return on assets	6.20%	6.70%