Postretirement Benefits (Schedule Of Changes In Benefit Obligations For Postretirement Welfare Plans) (Details) (Other Postretirement Benefit Plan, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Curtailments	$ (2)	$ 0
Benefit obligation at beginning of period	131	144
Service cost	2	2	2
Interest cost	5	6	7
Actuarial (gain) loss	(2)	(9)
Benefit payments	(15)	(12)
Benefit obligation at end of period (1)	$ 119	$ 131	$ 144