Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income Tax Disclosure [Abstract]
Deferred Income Tax Expense (Benefit)		$ 55
Effective tax rates	3.50%	10.50%	13.90%	20.70%
United States statutory tax rate	35.00%			35.00%
Effective tax rate for non-U.S. profits			0.00%	0.00%
Unrecognized Tax Benefits, Period Increase (Decrease)	9
Gross unrecognized tax benefits	283		283
Cash deposits to offset uncertain tax liabilities	43		43
Amount of unrecognized tax benefits that would affect the effective tax rate	102		102
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	168		168
Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued Increase Decrease	2
Combined amount of accrued interest and penalties related to uncertain tax positions	23		23
Amount of unrecognized tax benefits for which it is reasonably possible that there will be a reduction within the next 12 months	$ 81		$ 81