Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2013
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 19		$ 24		$ 16
Additions/(deductions) charged/(credited) to costs and expenses	1		4		9
Deductions	(3)	[1]	(9)	[1]	(1)	[1]
Balance at end of period	$ 17		$ 19		$ 24

[1] Write-off of amounts against allowance provided