Income Taxes, Reconciliation of U.S. Federal Statutory Rate to Effective Tax Rate (Details)	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Reconciliation of federal statutory income tax rate to company's effective income tax rate [Abstract]
Statutory federal tax	21.00%	21.00%	31.50%
State taxes, net of federal benefit	(12.00%)	3.60%	2.90%
Taxes on non-U.S. earnings and losses	32.90%	3.90%	(3.80%)
Valuation allowances	156.90%	4.00%	(5.60%)
Tax credits	(36.70%)	(26.10%)	(17.30%)
Compensation	4.00%	(0.10%)	(0.80%)
Tax rate or law changes	3.60%	(12.00%)	60.10%
Uncertain tax positions, net of settlements	(37.90%)	0.40%	(0.80%)
Notional interest deductions	(12.50%)	(2.50%)	(3.20%)
Dividends and taxable foreign inclusions	(11.00%)	1.60%	0.20%
Other	10.90%	(0.10%)	(0.80%)
Effective tax rate	119.20%	(6.30%)	62.40%