Income Taxes (Schedule of Unrecognized Tax Benefits Roll Forward) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits – January 1	$ 939	$ 1,198	$ 1,787
Gross increases – tax positions in prior periods	55	154	95
Gross decreases – tax positions in prior periods	(20)	(383)	(465)
Gross increases – current-period tax positions	83	28	76
Gross decreases – current-period tax positions	(1)	(15)	(40)
Settlements	(1)	(42)	(254)
Lapse of statute of limitations		(1)	(1)
Unrecognized tax benefits – December 31	$ 1,055	$ 939	$ 1,198