Accumulated Other Comprehensive Income Effects on net income of amounts reclassified from accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (12)	$ 11	$ 9
Unrealized Gains (Losses) on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0
Unrealized Gains (Losses) on Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(12)	11	9
Unrealized Gains (Losses) on Derivative Instruments | Sales Revenue, Net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(23)	(2)	7
Unrealized Gains (Losses) on Derivative Instruments | Research and Development
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 11	$ 13	$ 2