Income Taxes (Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Accruals, reserves and other expenses	$ 151	$ 171
Tax credit carryforwards	276	334
Stock-based compensation	37	39
Net operating loss & capital loss carryforwards	25	28
Total	489	572
Valuation allowance	(114)	(114)
Deferred tax assets, net of valuation allowance	375	458
Amortization and Depreciation	(19)	(27)
Unremitted earnings of foreign subsidiaries	70	43
Prepaids and other liabilities	(1)	(3)
Total	(90)	(73)
Deferred tax assets, net of valuation allowance and deferred tax liabilities	$ 285	$ 385