Income Taxes (Deferred Tax Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Income Tax Disclosure [Abstract]
Accruals, reserves and other expenses	$ 179	$ 182
Tax credit carryforwards	214	201
Stock-based compensation	46	49
Unrealized gain on marketable equity securities	0	14
Net operating loss & capital loss carryforwards	286	273
Total	725	719
Valuation allowance	(510)	(487)
Deferred tax assets, net of valuation allowance	215	232
Depreciation	(16)	(19)
State effect on federal taxes	(56)	(52)
Amortization	(34)	(44)
Prepaids and other liabilities	(11)	(22)
Total	(117)	(137)
Deferred tax assets, net of valuation allowance and deferred tax liabilities	$ 98	$ 95