Income Taxes Income Taxes (Schedule of Net Deferred Tax Asset/Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets, Gross [Abstract]
Employee benefits	$ 111	$ 228
Operating loss carryforwards	1,030	1,065
Capital loss carryforwards	3	4
Foreign tax credits	611	4,430
Other credit carryforwards	0	35
Investments in subsidiaries and affiliates	174	91
Other	69	86
Deferred Tax Assets, Gross	1,998	5,939
Deferred Tax Assets, Valuation Allowance	(926)	(4,301)
Deferred Tax Assets, Net of Valuation Allowance	1,072	1,638
Deferred Tax Liabilities, Gross [Abstract]
Property, plant and equipment	1,332	3,672
Accrued revenue	81	75
Other	3	(7)
Deferred Tax Liabilities, Gross	1,416	3,740
Deferred Tax Liabilities, Net	$ 344	$ 2,102