Income Taxes (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Income Tax Disclosure [Abstract]        
Income tax expense $ 88 $ 81 $ 248 $ 60
Net discrete tax benefit recognized $ 6   $ 23 $ 184
Estimated annual effective tax rate, which excludes impact of discrete items     29.70% 28.80%
Expected fiscal year 2015 effective tax rate     28.00%