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Derivatives and Risk Management - Balance Sheet Location of Hedged Item (Details) - USD ($)
$ in Millions
Mar. 31, 2019
Dec. 31, 2018
Current maturities of long-term debt and finance leases    
Derivative [Line Items]    
Carrying amount of hedge instruments $ (16) $ (11)
Cumulative amount of fair value hedge adjustments 1 7
Long-term debt and finance leases    
Derivative [Line Items]    
Carrying amount of hedge instruments (1,878) (1,870)
Cumulative amount of fair value hedge adjustments $ (25) $ (8)