Income Taxes (Reconciliation of Beginning and Ending Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Unrecognized Tax Benefits
Balance at beginning of year	$ 262	$ 381	$ 399
Additions based on tax positions related to the current year	15	15	22
Additions for tax positions of prior years	35	170	71
Reductions for tax positions due to lapse of statutes of limitations	(1)	(16)	(39)
Reductions for tax positions of prior years	0	(102)	(67)
Settlements	(84)	(186)	(5)
Balance at end of year	$ 227	$ 262	$ 381