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Leases - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Jan. 01, 2019
Lessee, Lease, Description [Line Items]      
Lease assets $ 127    
Lease liabilities 124    
Lease income $ 14 $ 10  
Minimum      
Lessee, Lease, Description [Line Items]      
Operating lease, term of contract 2 years    
Maximum      
Lessee, Lease, Description [Line Items]      
Operating lease, term of contract 10 years    
Accounting Standards Update 2016-02      
Lessee, Lease, Description [Line Items]      
Lease assets     $ 68
Lease liabilities     $ 66