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Leases - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Leases [Abstract]      
Lease term extension 15 years    
Termination period one year    
Operating lease expense under ASC 842 $ 171 $ 162  
Operating lease expense under ASC 840     $ 109