Property, Plant and Equipment (Depreciation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Property, Plant and Equipment [Line Items]
Fully depreciated assets	$ 1
Depreciation expense related to property, plant and equipment, net	$ 299	$ 294	$ 294