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Leases - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2018
Lessee, Lease, Description [Line Items]    
Option to extend leases 6 years  
Rent expense under prior lease accounting rules (ASC 840)   $ 260
Minimum    
Lessee, Lease, Description [Line Items]    
Remaining term of leases 1 year  
Maximum    
Lessee, Lease, Description [Line Items]    
Remaining term of leases 19 years