Income Taxes (Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Accruals, reserves and other expenses	$ 81	$ 151
Tax credit carryforwards	121	276
Stock-based compensation	24	37
Net operating loss & capital loss carryforwards	23	25
Total	249	489
Valuation allowance	(138)	(114)
Deferred tax assets, net of valuation allowance	111	375
Amortization and Depreciation	(27)	(19)
Unremitted earnings of foreign subsidiaries	0	70
Prepaids and other liabilities	(2)	(1)
Total	(29)	(90)
Deferred tax assets, net of valuation allowance and deferred tax liabilities	$ 82	$ 285