Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts - USD ($) $ in Millions		12 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		$ 17	$ 19	$ 24
Additions/(deductions) charged/(credited) to costs and expenses		(2)	1	4
Deductions	[1]	(6)	(3)	(9)
Balance at end of period		$ 9	$ 17	$ 19

[1] Write-off of amounts against allowance provided