Commitments and Contingencies (Lease Disclosures) (Detail) $ in Millions	Dec. 31, 2020 USD ($)
Operating lease liability	us-gaap:OperatingLeaseLiability
Operating lease weighted average remaining lease term	8 years 3 months 18 days
Operating lease weighted average discount rate percent	7.50%
Operating leases future minimum payments due	$ 29
Other Assets [Member]
Operating lease right of use asset	20
Other Liabilities [Member]
Operating lease liability	$ 20