Stock-Based Compensation And Employee Benefit Plans (Schedule of Share Repurchases) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Nov. 04, 2020	May 11, 2018	May 08, 2017
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 729	$ 1,207	$ 1,192
May 2017 Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount						$ 1,200
Stock Repurchased and Retired During Period, Value			$ 76
Stock repurchased and retired during period, Shares			0.6
May 2018 Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 2,400
Stock Repurchased and Retired During Period, Value	$ 78	$ 1,207	$ 1,116
Stock repurchased and retired during period, Shares	0.7	12.3	10.4
November 2020 Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 2,600
Stock Repurchased and Retired During Period, Value	$ 651
Stock repurchased and retired during period, Shares	4.9
Repurchase program, total
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 729	$ 1,207	$ 1,192
Stock repurchased and retired during period, Shares	5.6	12.3	11.0