Income Taxes Net Unrecognized Tax Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 265	$ 308
Additions based on tax positions related to the current year	81	15
Additions for tax positions of prior years	54	15
Reductions for tax positions of prior years	(90)	(58)
Statute of limitations	(68)	(12)
Settlements	(8)	0
Interest and penalties	(11)	(3)
Ending balance	223	265
Unrecognized tax benefits that would impact effective tax rate	113	156
Unrecognized tax benefits that would not impact the effective tax rate	$ 110	$ 109