Leases - Summary of Supplemental Balance Sheet Information Related to Operating Leases (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Other assets	$ 36	$ 36
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets (Note 11)	Other assets (Note 11)
Accrued liabilities	$ 5	$ 5
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued liabilities (Note 12)	Accrued liabilities (Note 12)
Other liabilities	$ 14	$ 15
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other liabilities (Note 13)	Other liabilities (Note 13)
Liabilities subject to compromise	$ 17	$ 19
Weighted-average lease term (in years)	5 years 7 days	5 years 1 month 20 days
Weighted-average discount rate	6.18%	6.16%