Leases - Maturity Analysis of Finance and Operating Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finance Leases, After Adoption of 842:
2021	$ 10
2022	0
Total lease payments	10
Less imputed interest	(1)
Finance, present value of lease liabilities	9	$ 18
Less current maturities	(9)	(9)
Present value of lease liabilities, less current maturities	0	9
Operating Leases, After Adoption of 842:
2021	28
2022	2
Total lease payments	30
Less imputed interest	(1)
Operating, present value of lease liabilities	29	25
Less current maturities	(27)	(9)
Present value of lease liabilities, less current maturities	$ 2	$ 16