Income Taxes (Net Deferred Tax Assets and Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Components of Deferred Tax Assets and Liabilities [Abstract]
Deferred tax assets	$ 16,580		$ 16,181
Deferred tax liabilities	(14,046)		(12,939)
Valuation allowance	(121)		(101)
Net deferred tax assets	$ 2,413	[1]	$ 3,141	[1]

[1] Of the deferred tax asset for net operating loss and credit carryovers, $201 expires in years ending from December 31, 2013 through December 31, 2032 and $106 may be carried over indefinitely.