Derivatives and Risk Management - Balance Sheet Location of Hedged Item (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Current maturities of long-term debt and finance leases
Derivative [Line Items]
Carrying amount of hedge instruments	$ (20)	$ (11)
Cumulative amount of fair value hedge adjustments	7	7
Long-term debt and finance leases
Derivative [Line Items]
Carrying amount of hedge instruments	(1,759)	(1,870)
Cumulative amount of fair value hedge adjustments	$ 75	$ (8)