Acquisition and Restructuring Costs (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended			29 Months Ended	3 Months Ended	12 Months Ended			26 Months Ended	3 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended		16 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Business Operations And Information Technology Transformation Program	Mar. 31, 2012 Business Operations And Information Technology Transformation Program	Dec. 31, 2012 Business Operations And Information Technology Transformation Program	Dec. 31, 2011 Business Operations And Information Technology Transformation Program	Dec. 31, 2010 Business Operations And Information Technology Transformation Program	Mar. 31, 2013 Business Operations And Information Technology Transformation Program	Mar. 31, 2013 Business Operations And Information Technology Transformation Program Involuntarily Terminated [Member] employees	Dec. 31, 2012 Business Operations And Information Technology Transformation Program Involuntarily Terminated [Member] employees	Dec. 31, 2011 Business Operations And Information Technology Transformation Program Involuntarily Terminated [Member] employees	Dec. 31, 2010 Business Operations And Information Technology Transformation Program Involuntarily Terminated [Member] employees	Dec. 31, 2012 Business Operations And Information Technology Transformation Program Involuntarily Terminated [Member] employees	Mar. 31, 2012 Expenses Control Measures	Dec. 31, 2012 Expenses Control Measures	Dec. 31, 2011 Expenses Control Measures	Mar. 31, 2013 Expenses Control Measures Involuntarily Terminated [Member] employees	Dec. 31, 2012 Expenses Control Measures Involuntarily Terminated [Member] employees	Dec. 31, 2011 Expenses Control Measures Involuntarily Terminated [Member] employees	Mar. 31, 2013 Expenses Control Measures Involuntarily Terminated [Member] employees	Mar. 31, 2013 Expenses Control Measures - Additional Targeted Staff Reductions	Dec. 31, 2011 Expenses Control Measures - Additional Targeted Staff Reductions	Mar. 31, 2013 Expenses Control Measures - Additional Targeted Staff Reductions Involuntarily Terminated [Member] employees	Dec. 31, 2012 Expenses Control Measures - Additional Targeted Staff Reductions Involuntarily Terminated [Member] employees	Mar. 31, 2013 Expenses Control Measures - Additional Targeted Staff Reductions Involuntarily Terminated [Member] employees
Business Acquisition [Line Items]
Acquisition costs	$ 15	$ 13
Restructuring charges, net	$ (1)	$ 8	$ 8	$ 15	$ 67	$ 133	$ 156	$ 364						$ (7)	$ (1)	$ 120					$ (9)	$ 133
Expected number of positions eliminated									148	164	530	1,400	2,242						442					630
Percent of actual number of positions eliminated												5.00%
Actual number of positions eliminated									36	697	782	550	2,065				6	363	15	384			413	40	453