Income Taxes (Unrecognized Tax Benefits Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 34	$ 37	$ 39
Additions based on tax positions related to the current period	5	6	7
Additions based on tax positions of prior years	0	3	3
Reductions based on tax positions of prior years	0	(6)	(1)
Settlements	(1)	(10)	(3)
Foreign exchange	(2)	4	(8)
Ending Balance	$ 36	$ 34	$ 37