Income Taxes (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Components of Deferred Tax Assets [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	$ 6,414	$ 6,647
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits	6,415	5,703
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	402	402
Deferred Tax Assets, Deferred Income	2,133	2,297
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Deferred Rent	233	284
Deferred Tax Assets Reorganization Items	209	395
Deferred Tax Assets, Other	439	564
Deferred Tax Assets, Valuation Allowance	(10,963)	(10,705)
Deferred Tax Assets, Net	5,282	5,587
Components of Deferred Tax Liabilities [Abstract]
Deferred Tax Liabilities, Property, Plant and Equipment	4,851	5,093
Deferred Tax Liabilities, Financing Arrangements	162	206
Deferred Tax Liabilities, Goodwill and Intangible Assets, Intangible Assets	1,730	1,755
Deferred Tax Liabilities, Derivatives	31	32
Deferred Tax Liabilities, Other	92	68
Deferred Tax Liabilities	6,866	7,154
Deferred Tax Assets, Net, Classification [Abstract]
Deferred Tax Assets (Liabilities), Net, Current	463	461
Deferred Tax Assets (Liabilities), Net, Noncurrent	(2,047)	(2,028)
Deferred Tax Assets (Liabilities), Net	$ (1,584)	$ (1,567)