Derivative Financial Instruments - Summary of Effect of Foreign Currency Exchange Contracts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gains recognized in AOCI	$ 1	$ 119	$ 29	$ 58
Gains (losses) reclassified from AOCI into product sales	36	(45)	65	(93)
Gains (losses) recognized in Other income (expense), net	$ (5)	$ 10	$ (11)	$ (4)