Financial Instruments (Interest Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Interest expense, net of capitalized interest	$ 231	$ 223	$ 206
Capitalized interest expense	$ 17	$ 13	$ 9