Restructuring - Schedule of Accrued Restructuring Included in Accrued Expenses and Other Liabilities by Cost Type (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Restructuring Reserve [Roll Forward]
Costs charged to expense	$ 13		$ 6	$ 43	$ 29
Cumulative charges incurred through June 30, 2021	268			268
2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	104	$ 91		91
Costs charged to expense	17	27
Cash payments	(13)	(10)
Non-cash charge adjustment	12	4
Balance, ending	96	104		96
Cumulative charges incurred through June 30, 2021	263			263
Severance and employee related costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	101	88		88
Costs charged to expense	3	24
Cash payments	(11)	(9)
Non-cash charge adjustment	0	2
Balance, ending	93	101		93
Cumulative charges incurred through June 30, 2021	179			179
Facilities and related costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	0	0		0
Costs charged to expense	12	1
Cash payments	0	0
Non-cash charge adjustment	12	1
Balance, ending	0	0		0
Cumulative charges incurred through June 30, 2021	48			48
Other costs | 2019 Restructuring Plan
Restructuring Reserve [Roll Forward]
Balance, beginning	3	3		3
Costs charged to expense	2	2
Cash payments	(2)	(1)
Non-cash charge adjustment	0	1
Balance, ending	3	$ 3		3
Cumulative charges incurred through June 30, 2021	$ 36			$ 36