Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Impairments for assets held	$ 31	$ 6	$ 12	$ 39	$ 12	$ 14
Acquisition-Related Intangible Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of Intangible Assets, Finite-lived				39	12
Net Carrying Value [Member] | Acquisition-Related Intangible Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related intangible assets	4		0	4	0
Significant Unobservable Inputs (Level 3) [Member] | Acquisition-Related Intangible Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related intangible assets	$ 4			$ 4