Shared-Based Compensation - Narrative (Details) - USD ($) shares in Millions, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 29, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Class of Stock [Line Items]
Non-cash expense recognized		$ 32	$ 36	$ 105	$ 100
Acquisition costs		76	$ 0	$ 90	$ 1
Time Based Restricted Units
Class of Stock [Line Items]
Cost not yet recognized, period for recognition				3 years
Performance Based Restricted Stock Units
Class of Stock [Line Items]
Unrecognized compensation expense	$ 41	33		$ 33
Cost not yet recognized, period for recognition	3 years
Vested stock options (in shares)	0.5
Stock-based compensation		8		21
Amount of non-cash compensation remaining in fiscal period		8		8
Time Based And Performance Based Restricted Stock
Class of Stock [Line Items]
Unrecognized compensation expense		143		$ 143
Cost not yet recognized, period for recognition				1 year 6 months
Maximum | Performance Based Restricted Stock Units
Class of Stock [Line Items]
Unrecognized compensation expense	$ 82
Shares reserved for future issuance (in shares)	0.9
Employee Stock Option
Class of Stock [Line Items]
Unrecognized compensation expense		$ 10		$ 10
Cost not yet recognized, period for recognition				1 year 7 months 6 days
Bridge2 Solutions
Class of Stock [Line Items]
Acquisition costs				$ 10
Bridge2 Solutions | Bakkt
Class of Stock [Line Items]
Capital call amount				$ 300