Stock-Based Compensation And Employee Benefit Plans (Schedule of ESPP Activity) (Details) - Employee Stock [Member] - $ / shares shares in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, Employee Stock Purchase Plans	0.6	0.7	0.9
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 21.57	$ 17.93	$ 12.97
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Espp Exercise Price For Shares Issued	67.56	54.60	32.16
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Espp Exercise Price For Shares Issued	$ 99.82	$ 67.56	$ 54.78