Income Taxes - Earnings Before Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Domestic	$ (4,274)	$ (2,678)	$ (1,651)
Foreign	9,471	10,405	9,535
Total earnings before income tax expense	$ 5,197	$ 7,727	$ 7,884