Pension Benefits (Schedule Of Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income) (Details) (Defined Pension Benefit Plans [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Defined Pension Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 61	$ 10	$ 59
Prior service credit	0	0	(2)
Amortization of Net actuarial loss	(25)	(26)	(23)
Amortization of Prior service cost	(2)	(2)	(2)
Total recognized in net periodic benefit cost and other comprehensive loss (income)	$ 34	$ (18)	$ 32