Property, Plant and Equipment (Depreciation Expense, Software Amortization and Capitalized Interest) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1,105	$ 1,064	$ 1,154
Interest capitalized during development and construction	125	89	$ 118
Property plant and equipment, net of accumulated depreciation mortgaged, pledged or subject to liens	$ 10,000	$ 11,000