Other Commitments and Contingent Liabilities (Litigation Reserve and Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Loss Contingencies [Line Items]
Charges incurred	$ 68	$ 72	$ 149
Payments Made	(105)	(483)	(26)
Average Wholesale Price Litigation [Member]
Loss Contingencies [Line Items]
AWP Litigation Reserve, Beginning Balance	42	453	330
Charges incurred	68	72	149
Payments Made	(105)	(483)	(26)
AWP Litigation Reserve, Ending Balance	$ 5	$ 42	$ 453