Stockholders' Equity (Other Comprehensive Income (Loss), Tax (Phantom)(Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Stockholders' Equity Note [Abstract]
Foreign currency translation adjustments arising during period, net of income tax expense (benefit) of nil, nil and ($2)	$ 0	$ 0	$ (2)
Reclassified to income statement, income tax expense of nil, $24 and nil	0	24	0
Unrealized losses on cash flow hedges arising during period, tax benefit of nil, nil and nil	0	0	0
Reclassification to income statement, net of income tax expense of nil, nil and nil	0	0	0
Net actuarial gain (loss) arising during period, net of income tax (benefit) of ($66), $16 and ($22)	(66)	16	(22)
Amortization of actuarial loss, prior service cost and transition obligation, net of income tax (benefit) of $6, $12 and $12	6	12	12
Foreign currency translation adjustments, net of income tax expense of nil, nil and nil	0	0	0
Reclassified to income statement, income tax expense of nil, $1 and nil	$ 0	$ 1	$ 0