Employee Benefit Plans - Change in Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 953	$ 1,086	$ 978
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	(34)	80
Company contributions	24	25
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(86)	(75)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	(38)	77
Plan participant contributions	1	1
U.S. Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,269	1,444	1,722
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	(76)	149
Company contributions	0	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(99)	(427)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	0	0
Plan participant contributions	0	0
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,222	2,530	$ 2,700
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	(110)	229
Company contributions	24	25
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(185)	(502)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	(38)	77
Plan participant contributions	$ 1	$ 1