Restructuring - Schedule of Accrued Restructuring Included in Accrued Expenses and Other Liabilities by Cost Type (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Costs charged to expense	$ 94	$ 132	$ 10
Cumulative charges incurred to date	224
2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	35	0
Costs charged to expense	87	132
Cash payments	(25)	(56)
Non-cash charge adjustment	(6)	(41)
Balance, ending	91	35	0
Cumulative charges incurred to date	219
Severance and employee related costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	32	0
Costs charged to expense	76	76
Cash payments	(20)	(44)
Non-cash charge adjustment	0	0
Balance, ending	88	32	0
Cumulative charges incurred to date	152
Facilities and related costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	0	0
Costs charged to expense	6	29
Cash payments	0	0
Non-cash charge adjustment	(6)	(29)
Balance, ending	0	0	0
Cumulative charges incurred to date	35
Other costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	3	0
Costs charged to expense	5	27
Cash payments	(5)	(12)
Non-cash charge adjustment	0	(12)
Balance, ending	3	$ 3	$ 0
Cumulative charges incurred to date	$ 32