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Lease Operations Lease Operations (Narrative) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Leases [Abstract]      
Operating lease revenue, excluding executory costs $ 928 $ 601 $ 586
Operating leases of lessor contingent rentals received $ 9 $ 9 $ 7