Cost Reduction Programs and Other Charges - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Cost reduction programs and other charges	$ 249	$ 141	$ 380	$ 230
Cost reduction programs and other charges, after-tax and noncontrolling interest	187	113	282	194
Cost reduction program charges	213
Cost reduction program charges, net of tax	151		207
Other charges, merger related		65		121
Other charges, merger related, net of tax	36	52	75	105
Cash requirement for the cost reduction program and other charges	296		296
Severance costs
Restructuring Cost and Reserve [Line Items]
Cost reduction programs and other charges		76		109
Cost reduction programs and other charges, after-tax and noncontrolling interest		$ 61		$ 89
Merger-related and other charges
Restructuring Cost and Reserve [Line Items]
Cost reduction programs and other charges			89
Other charges, merger related	36		89
Cost Reduction Program
Restructuring Cost and Reserve [Line Items]
Cost reduction programs and other charges	213		291
Cost reduction program charges			291
Cost Reduction Program | Severance costs
Restructuring Cost and Reserve [Line Items]
Cost reduction programs and other charges	192		250
Cost Reduction Program | Other cost reduction charges
Restructuring Cost and Reserve [Line Items]
Cost reduction programs and other charges	$ 21		$ 41