Financial Instruments (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011		Mar. 31, 2010
Financial Instruments [Line Items]
Cash and cash equivalents	$ 1,242,000,000	$ 1,353,000,000	$ 1,242,000,000	$ 1,353,000,000	$ 1,579,000,000	[1]	$ 1,273,000,000
Total impairments of marketable securities	0	0	0
Contractual interest rate of 0.75% Convertible Senior Notes due 2016	0.75%		0.75%
Proceeds from sale of marketable equity securities	0	0	0	132,000,000
The9 [Member]
Financial Instruments [Line Items]
Total impairments of marketable securities				2,000,000
Proceeds from sale of investment				11,000,000
Gain (loss) on sale of investment				(3,000,000)
Ubisoft [Member]
Financial Instruments [Line Items]
Proceeds from sale of investment				121,000,000
Gain (loss) on sale of investment				$ 28,000,000
0.75% Convertible Senior Notes Due 2016 [Member]
Financial Instruments [Line Items]
Contractual interest rate of 0.75% Convertible Senior Notes due 2016	0.75%		0.75%

[1] Derived from audited consolidated financial statements.