Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Line Items]
Other Tax Benefit	$ 41
Deferred Tax Assets, Valuation Allowance	100.00%
Stock Repurchased and Retired During Period, Value	$ 1,018	$ 337
Tax Benefits Allocated Directly to Contributed Capital	83	21	$ 12
Valuation allowance decrease		441
Gross unrecognized tax benefits	331	254	$ 232	$ 297
Amount of unrecognized tax benefits that would affect the effective tax rate	305
The total amount of unrecognized tax benefits that, if recognized, would result in adjustments to deferred tax assets with corresponding	26
Combined amount of accrued interest and penalties related to uncertain tax positions	15	16
Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued Increase Decrease	1
Amount of unrecognized tax benefits for which it is reasonably possible that there will be a reduction within the next 12 months	50
Unremitted earnings of foreign subsidiaries	43	0
Deferred Tax Assets, Valuation Allowance	114	555
Internal Revenue Service (IRS) [Member]
Income Tax Disclosure [Line Items]
Tax credit carry forwards	$ 373
Tax credit carryforward, expiration dates	Jan. 01, 2024
Foreign Country [Member]
Income Tax Disclosure [Line Items]
Undistributed Earnings of Foreign Subsidiaries	$ 1,241
Tax credit carry forwards	8
State [Member]
Income Tax Disclosure [Line Items]
Net operating Loss Carryforwards	1,016
Net operating loss attributable to various acquired companies	130
Tax credit carry forwards	93
Fiscal Year 2016 Repurchase Program [Member]
Income Tax Disclosure [Line Items]
Stock Repurchased and Retired During Period, Value	$ 500	$ 0