Cost Reduction Programs and Other Charges - Summary of Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			$ 369
2021 Cost Reduction Programs and Other Charges	$ 204	$ 249	196	$ 380
Less: Cash payments			(96)
Less: Non-cash charges / benefits			35
Foreign currency translation and other			(8)
Balance, June 30, 2021	496		496
Severance costs
Restructuring Reserve [Roll Forward]
2021 Cost Reduction Programs and Other Charges		$ 192		$ 250
Merger-related and other charges
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			64
2021 Cost Reduction Programs and Other Charges	0		(52)
Less: Cash payments			(6)
Less: Non-cash charges / benefits			54
Foreign currency translation and other			(3)
Balance, June 30, 2021	57		57
Cost Reduction Program
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			305
2021 Cost Reduction Programs and Other Charges	204		248
Less: Cash payments			(90)
Less: Non-cash charges / benefits			(19)
Foreign currency translation and other			(5)
Balance, June 30, 2021	439		439
Cost Reduction Program | Severance costs
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			283
2021 Cost Reduction Programs and Other Charges	182		208
Less: Cash payments			(85)
Less: Non-cash charges / benefits			0
Foreign currency translation and other			(5)
Balance, June 30, 2021	401		401
Cost Reduction Program | Other cost reduction charges
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			22
2021 Cost Reduction Programs and Other Charges	22		40
Less: Cash payments			(5)
Less: Non-cash charges / benefits			(19)
Foreign currency translation and other			0
Balance, June 30, 2021	$ 38		$ 38