Cost Reduction Programs and Other Charges - Summary of Activity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			$ 369
2021 Cost Reduction Programs and Other Charges	$ 26	$ 48	222	$ 428
Less: Cash payments			(139)
Less: Non-cash charges / benefits			33
Foreign currency translation and other			(19)
Balance, September 30, 2021	466		466
Severance costs
Restructuring Reserve [Roll Forward]
2021 Cost Reduction Programs and Other Charges		$ 31		$ 281
Merger-related and other charges
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			64
2021 Cost Reduction Programs and Other Charges	(3)		(55)
Less: Cash payments			(17)
Less: Non-cash charges / benefits			54
Foreign currency translation and other			0
Balance, September 30, 2021	46		46
Cost Reduction Program
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			305
2021 Cost Reduction Programs and Other Charges	29		277
Less: Cash payments			(122)
Less: Non-cash charges / benefits			(21)
Foreign currency translation and other			(19)
Balance, September 30, 2021	420		420
Cost Reduction Program | Severance costs
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			283
2021 Cost Reduction Programs and Other Charges	20		228
Less: Cash payments			(113)
Less: Non-cash charges / benefits			0
Foreign currency translation and other			(14)
Balance, September 30, 2021	384		384
Cost Reduction Program | Other cost reduction charges
Restructuring Reserve [Roll Forward]
Balance, December 31, 2020			22
2021 Cost Reduction Programs and Other Charges	9		49
Less: Cash payments			(9)
Less: Non-cash charges / benefits			(21)
Foreign currency translation and other			(5)
Balance, September 30, 2021	$ 36		$ 36