Pension and Other Benefit Plans - Asset Allocations (Details) - Pension Plans, Defined Benefit	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Percent of plan assets	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Percent of plan assets	19.00%	19.00%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Percent of plan assets	42.00%	46.00%
Alternatives
Defined Benefit Plan Disclosure [Line Items]
Percent of plan assets	37.00%	31.00%
Cash and other
Defined Benefit Plan Disclosure [Line Items]
Percent of plan assets	2.00%	4.00%