Stockholders' Equity (Other Comprehensive Income (Loss), Net of Tax) (Parentheticals) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Stockholders' Equity Attributable to Parent [Abstract]
Foreign currency translation adjustments arising during period, income tax expense (benefit) of ($2), ($2), nil and $2	$ (2)	$ (2)	$ 0	$ 2
Reclassified to income statement, income tax expense of $24, nil, $24 and nil	24	0	24	0
Unrealized gains (losses) on cash flow hedges arising during period, income tax expense of nil, nil, nil and nil	0	0	0	0
Amortization of actuarial loss, prior service cost and transition obligation, income tax expense of $2, $2, $6 and $5	2	2	6	5
Foreign currency translation adjustments, income tax expense of nil, nil, nil and nil	0	0	0	0
Reclassified to income statement, income tax expense of $1, nil, $1 and nil	$ 1	$ 0	$ 1	$ 0