Leases - Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease right-of-use assets	$ 4	$ 4
Finance lease assets	16	17
Total lease assets	20	21
Current finance lease liabilities	1	1
Operating lease liabilities	4	4
Finance lease liabilities	24	24
Total lease liabilities	29	29
Finance lease, accumulated amortization	$ 8	$ 6
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentNet	us-gaap:PropertyPlantAndEquipmentNet
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent