Employee Benefit Plans Employee Benefit Plans (Obligations, Funded Status, and Periodic Benefit Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	$ 11,950	$ 10,591	$ 11,409
Estimated fair value of plan assets	10,230	8,948	9,688
Over (under) funded status	(1,720)	(1,643)
Net periodic benefit costs	336	259	349
Pension Benefits | U.S.
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	10,824	9,580
Estimated fair value of plan assets	9,742	8,615
Over (under) funded status	(1,082)	(965)
Net periodic benefit costs	244	176
Pension Benefits | Non- U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	1,126	1,011
Estimated fair value of plan assets	488	333
Over (under) funded status	(638)	(678)
Net periodic benefit costs	92	83
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	1,289	1,324	1,674
Estimated fair value of plan assets	1,468	1,360	1,434
Over (under) funded status	179	36
Net periodic benefit costs	(67)	(64)	$ (10)
Other Postretirement Benefits | U.S.
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	1,247	1,288
Estimated fair value of plan assets	1,441	1,334
Over (under) funded status	194	46
Net periodic benefit costs	(70)	(66)
Other Postretirement Benefits | Non- U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations	42	36
Estimated fair value of plan assets	27	26
Over (under) funded status	(15)	(10)
Net periodic benefit costs	$ 3	$ 2