Stock-Based Compensation And Employee Benefit Plans (Schedule of ESPP Activity) (Details) - Employee Stock [Member] - $ / shares shares in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Employee Stock Purchase Plans	0.5	0.6	0.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 31.88	$ 21.57	$ 17.93
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Espp Exercise Price For Shares Issued	89.46	67.56	54.60
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Espp Exercise Price For Shares Issued	$ 107.51	$ 99.82	$ 67.56