Financial Instruments - Non-U.S. Dollar Debt Designated as Net Investment Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Euro notes
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains/(losses) related to hedges of net investments in international operations	$ 111	$ 18	$ 133	$ 94
British pound sterling notes
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains/(losses) related to hedges of net investments in international operations	8	5	9	13
Swiss franc notes
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains/(losses) related to hedges of net investments in international operations	24	(10)	16	6
Canadian dollar notes
Derivative Instruments, Gain (Loss) [Line Items]
After-tax gains/(losses) related to hedges of net investments in international operations	$ 4	$ (6)	$ (10)	$ (2)