Commitments and Contingent Liabilities (Litigation Reserve and Expense) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Loss Contingencies [Line Items]
Charges incurred	$ 15	$ 16
Payments made	(20)	(273)
Average Wholesale Price Litigation [Member]
Loss Contingencies [Line Items]
AWP litigation reserve at beginning of period	42	453
Charges incurred	15	16
Payments made	(20)	(273)
AWP litigation reserve at end of period	$ 37	$ 196