Income Tax Provision (Components of Income Tax Expense and Effective Income Tax Rate Reconciliation ) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Deferred
Total Deferred			$ 399	$ 231
Provision for income taxes	$ 176	$ 149	$ 389	$ 202
Reconciliation Between U.S. Federal Statutory Tax Rate and Effective Tax Rate
Effective tax rate	38.00%	38.00%	37.00%	38.00%