Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Deferred Tax Liability Not Recognized [Line Items]
Deferred income tax asset	$ 90	$ 139
Deferred income tax liabilities	2,807	3,484
Accrued liability for interest related to uncertain tax positions	6
Deferred Tax Assets, Operating Loss Carryforwards, windfalls	21
Operating Loss Carryforwards	1,096
Treasury Regulations Purchase of Stock	.05
Operating Loss Carrying Forwards Alternative Minimum Tax Amt	51
Operating Loss Carryforwards, Limitations on Use	.50
Unrecognized Tax Benefits	599	369
Less Other Non-Current Tax Liabilities [Member]
Deferred Tax Liability Not Recognized [Line Items]
Deferred income tax liabilities		$ 3,238