Restructuring and Related Reorganization Charges - Summary of the Restructuring and Related Reorganization Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Accrued liability as of January 1, 2020	$ 17,000,000
Charges	231,000,000	$ 24,000,000	$ 0
Payments	(137,000,000)
Non-cash items	(8,000,000)
Accrued liability as of December 31, 2020	103,000,000	17,000,000
Employee Severance and Benefits
Restructuring Reserve [Roll Forward]
Accrued liability as of January 1, 2020	11,000,000
Charges	205,000,000
Payments	(120,000,000)
Non-cash items	7,000,000
Accrued liability as of December 31, 2020	103,000,000	11,000,000
Other
Restructuring Reserve [Roll Forward]
Accrued liability as of January 1, 2020	6,000,000
Charges	26,000,000
Payments	(17,000,000)
Non-cash items	(15,000,000)
Accrued liability as of December 31, 2020	$ 0	$ 6,000,000