Income Tax (Reconciliation of 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 period	$ 708	$ 679	$ 810
Additions for tax positions of prior years	117	105	30
Reductions for tax positions of prior years	(37)	(82)	(161)
Additions for tax positions of current year	39	32	13
Reductions for tax positions of current year	(1)	(9)	(8)
Settlements with tax authorities	(52)	(15)	(5)
Lapses of statutes of limitations	0	(2)	0
Balance at end of the period	774	708	679
Unrecognized tax benefits that, if recognized would impact the effective rate	$ 661	$ 566	$ 527