Shareholders' Equity (Schedule of changes in AOCI by component) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Accumulated Translation Adjustment [Member]	Mar. 31, 2013 Unrealized Gains and Losses on Certain Investments	Dec. 31, 2012 Unrealized Gains and Losses on Certain Investments	Mar. 31, 2013 Unrealized Gains and Losses on Derivative Instruments	Mar. 31, 2013 Defined Benefit Pension Plans and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance January 1, 2013	$ (17,416)	$ 214	$ (8)	$ (8)	$ 86	$ (17,708)
OCI before reclassifications	(17)	(23)			(26)	32
Amounts reclassified from AOCI	392				2	390
Net current period OCI	375	(23)			(24)	422
Balance March 31, 2013	$ (17,041)	$ 191	$ (8)	$ (8)	$ 62	$ (17,286)