Long-term Debt and Interest Expense (Interest Expenses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Cash payments for interest	$ 117	$ 133	$ 164
Amortization of issuance discounts	1	1	1
Amortization of capitalized loan fees	4	4	4
Net changes in accruals	0	(6)	(9)
Interest incurred	126	132	160
Less capitalized interest	(5)	(6)	(7)
Total interest expense	$ 121	$ 126	$ 153