Restructuring and Related Reorganization Charges - Summary of the Restructuring and Related Reorganization 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]
Accrued liability as of January 1, 2021			$ 103
Charges	$ 13	$ 53	42	$ 128
Payments			(57)
Non-cash items			(17)
Accrued liability as of June 30, 2021	71		71
Employee Severance and Benefits
Restructuring Reserve [Roll Forward]
Accrued liability as of January 1, 2021			103
Charges			19
Payments			(53)
Non-cash items			(3)
Accrued liability as of June 30, 2021	66		66
Other
Restructuring Reserve [Roll Forward]
Accrued liability as of January 1, 2021			0
Charges			23
Payments			(4)
Non-cash items			(14)
Accrued liability as of June 30, 2021	$ 5		$ 5