Pension Benefits (Schedule Of Net Periodic Expense For Pension Plans) (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]
Service cost-benefits earned during the year	$ 7	$ 6	$ 4
Interest cost on projected benefit obligation	31	31	35
Expected return on assets	(31)	(29)	(24)
Amortization of unrecognized actuarial loss, prior service costs and net transitional obligation	27	28	25
Net periodic expense (income)	$ 34	$ 36	$ 40