Stock-Based Compensation And Employee Benefit Plans Stock-Based Compensation and Employee Benefits Plans (Schedule of Share Repurchases) (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended		17 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Jun. 30, 2012
Equity [Abstract]
Stock Repurchased and Retired During Period, Value		$ (471)
February 2011 Repurchase Program [Member]
Equity [Abstract]
Stock repurchased and retired during period, Shares	4,000	25,000	32,000
Stock Repurchased and Retired During Period, Value	(71)	(471)
July 2012 Repurchase Program [Member]
Equity [Abstract]
Stock repurchased and retired during period, Shares	22,000
Stock Repurchased and Retired During Period, Value	(278)
Repurchase Program, Total [Member]
Equity [Abstract]
Stock repurchased and retired during period, Shares	26,000	25,000
Stock Repurchased and Retired During Period, Value	$ 349	$ (471)