Property, Plant and Equipment (Depreciation Expense, Software Amortization and Capitalized Interest) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1,004	$ 977	$ 960
Interest capitalized during development and construction	307	$ 238	$ 199
Property plant and equipment, net of accumulated depreciation mortgaged, pledged or subject to liens	$ 10,000