Income Tax Provision (Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Change in Unrecognized Tax Benefits
Balance at beginning of the period	$ 8	$ 6	$ 39
Increases related to positions taken during the prior years	0	2	0
Increases related to positions taken during the current year	1	0	0
Decreases related to positions taken during the prior years	0	0	0
Decreases related to positions taken during the current year	0	0	0
Settlements	(2)	0	(33)
Expiration of statute of limitations	0	0	0
Balance at end of period	$ 7	$ 8	$ 6

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The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

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The gross amount of decreases in unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return for the current period, excluding amounts pertaining to examined tax returns.

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The gross amount of decreases in unrecognized tax benefits resulting from settlements with taxing authorities.

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The gross amount of decreases in unrecognized tax benefits resulting from lapses of the applicable statutes of limitations.

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