Financial Instruments (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Mar. 31, 2011		Mar. 31, 2010
Financial Instruments [Line Items]
Cash and cash equivalents	$ 930,000,000	$ 1,056,000,000	$ 930,000,000	$ 1,056,000,000	$ 1,579,000,000	[1]	$ 1,273,000,000
Total impairments of marketable securities	0	0	0
Proceeds from sale of investment	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	132,000,000
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%
The9 [Member]
Financial Instruments [Line Items]
Total impairments of marketable securities				2,000,000
Proceeds from sale of investment		3,000,000		11,000,000
Gain (loss) on sale of investment		1,000,000		(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

[1] Derived from audited consolidated financial statements.