Debt and Finance Lease Obligations, Interest Incurred (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest and Debt Expense, Net of Capitalized Interest
Interest and debt expense	$ 638	$ 544	$ 557
Less: Capitalized interest	75	90	87
Interest and debt expense, net of capitalized interest	$ 563	$ 454	$ 470