Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Income Taxes (Textual) [Abstract]
Income tax (benefit) expense	$ (118)	$ 130
Net discrete tax benefit recognized primarily from completion of federal income tax returns examination	181
Estimated annual effective tax rate, which excludes impact of discrete items	29.10%	32.40%
Expected fiscal year 2014 effective tax rate	14.00%
Reduction in uncertain tax positions resulting from completion of federal income tax returns examination	221
Cash refund expected from completion of federal income tax returns examination	$ 70