Pension Benefits (Schedule Of Net Periodic Expense For Pension Plans) (Details) (Pension Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost-benefits earned during the year	$ 7	$ 7	$ 6
Interest cost on projected benefit obligation	28	31	31
Expected return on assets	(28)	(31)	(29)
Amortization of unrecognized actuarial loss, prior service costs and net transitional obligation	32	27	28
Net periodic expense (income)	$ 39	$ 34	$ 36