Income Taxes (Schedule of Components of Net Provisions Related To Special Items) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Tax Special Items [Line Items]
Income tax provision (benefit) related to special items	$ (453)	$ (869)	$ (63)
Special Items [Member]
Tax Special Items [Line Items]
Income tax provision (benefit) related to special items	(372)	(95)	(82)
Internal Restructuring [Member]
Tax Special Items [Line Items]
Income tax provision (benefit) related to special items	(90)	(4)	14	(90)	2
Settlement with Taxing Authority [Member]
Tax Special Items [Line Items]
Income tax provision (benefit) related to special items	10	(770)	0			10
Valuation Allowance of Deferred Tax Assets [Member]
Tax Special Items [Line Items]
Income tax provision (benefit) related to special items	0	0	5
Tax Adjustments, Settlements, Unusual Provisions [Member]
Tax Special Items [Line Items]
Income tax provision (benefit) related to special items	$ (1)	$ 0	$ 0