Debt, Interest Incurred (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Interest and Debt Expense, Net of Capitalized Interest
Interest and debt expense	$ 145	$ 136
Less: Capitalized interest	20	24
Interest and debt expense, net of capitalized interest	$ 125	$ 112