Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2011
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 16		$ 22		$ 24
Additions/(deductions) charged/(credited) to costs and expenses	9		(1)		6
Deductions	(1)	[1]	(5)	[1]	(8)	[1]
Balance at end of period	$ 24		$ 16		$ 22

[1] Write-off of amounts against allowance provided