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Leases (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Lessee, Lease, Description [Line Items]        
Operating lease expense $ 1 $ 1 $ 2 $ 3
Lease not yet commenced, amount $ 7   $ 7  
Maximum [Member]        
Lessee, Lease, Description [Line Items]        
Leases, Remaining Lease Term Years     14 years  
Leases, Renewal Term     5 years  
Leases, not yet commenced, term 7 years   7 years  
Minimum [Member]        
Lessee, Lease, Description [Line Items]        
Leases, Remaining Lease Term Years     1 year  
Leases, not yet commenced, term 3 years   3 years