Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Income Tax Footnote Disclosure [Line Items]
Deferred Tax Assets, Valuation Allowance	$ 539
Effective tax rates	13.20%	5.40%
United States statutory tax rate	35.00%
Excess Tax Benefit from Share-based Compensation, Financing Activities	$ 40	$ 12
Unrecognized tax benefits, period increase (decrease)	6
Gross unrecognized tax benefits	260
Amount of unrecognized tax benefits that would affect the effective tax rate	58
The total amount of unrecognized tax benefits that, if recognized, would result in adjustments to deferred tax assets with corresponding adjustments to the valuation allowance	202
Unrecognized tax benefits income tax penalties and interest accrued increase (decrease)	1
Combined amount of accrued interest and penalties related to uncertain tax positions	17
Maximum
Income Tax Footnote Disclosure [Line Items]
Amount of unrecognized tax benefits for which it is reasonably possible that there will be a reduction within the next 12 months	$ 9