Interest Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Expense [Abstract]
Interest expense before capitalization	$ 339	$ 351	$ 335
Capitalized interest	(15)	(11)	(14)
Interest Expense	324	340	321
Interest paid, net	$ 315	$ 324	$ 331