Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Jan. 18, 2011
Operating Loss Carryforwards [Line Items]
Effective tax rates	10.50%	7.70%	20.70%	16.00%
United States statutory tax rate	35.00%		35.00%
Reduction in income tax expense	$ (40)	$ (17)	$ (31)	$ (20)
Recorded increase in gross unrecognized tax benefits	3		8
Gross unrecognized tax benefits	281		281
Amount of unrecognized tax benefits that would affect the effective tax rate	140		140
The total amount of unrecognized tax benefits that, if recognized, would result in adjustments to deferred tax assets with corresponding adjustments to the valuation allowance	128
Increase in accrued interest and penalties related to uncertain tax positions	1
Combined amount of accrued interest and penalties related to uncertain tax positions	24		24
Incremental tax liability asserted by jurisdiction					44
Amount of unrecognized tax benefits for which it is reasonably possible that there will be a reduction within the next 12 months	60		60
Effective tax rate for non-U.S. profits	0.00%
Popcap [Member]
Operating Loss Carryforwards [Line Items]
Net deferred tax liabilities	55		55
Popcap [Member] | Valuation Allowance Release [Member]
Operating Loss Carryforwards [Line Items]
Reduction in income tax expense	55
Tax Authority Deposit [Member]
Operating Loss Carryforwards [Line Items]
Deposits	$ 43		$ 43