Restructuring - Schedule of Accrued Restructuring Included in Accrued Expenses and Other Liabilities by Cost Type (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Costs charged to expense	$ 3			$ 9	$ 46	$ 39
Cumulative charges incurred through September 30, 2021	272				272
2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	96	$ 104	$ 91		91
Costs charged to expense	4	17	27
Cash payments	(18)	(13)	(10)
Non-cash charge adjustment	(3)	(12)	(4)
Balance, ending	79	96	104		79
Cumulative charges incurred through September 30, 2021	267				267
Severance and employee related costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	93	101	88		88
Costs charged to expense	1	3	24
Cash payments	(17)	(11)	(9)
Non-cash charge adjustment	(1)	0	(2)
Balance, ending	76	93	101		76
Cumulative charges incurred through September 30, 2021	180				180
Facilities and related costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	0	0	0		0
Costs charged to expense	2	12	1
Cash payments	0	0	0
Non-cash charge adjustment	(2)	(12)	(1)
Balance, ending	0	0	0		0
Cumulative charges incurred through September 30, 2021	50				50
Other costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	3	3	3		3
Costs charged to expense	1	2	2
Cash payments	(1)	(2)	(1)
Non-cash charge adjustment	0	0	(1)
Balance, ending	3	$ 3	$ 3		3
Cumulative charges incurred through September 30, 2021	$ 37				$ 37