Restructuring - Changes in Restructuring Liability (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021 USD ($)
Employee Severance
Restructuring Reserve [Roll Forward]
Restructuring liability, Beginning Balance	$ 18
Restructuring liability, Ending Balance	12
2020 MA Strategic Reorganization Restructuring Program
Restructuring Reserve [Roll Forward]
Restructuring liability, Ending Balance	12
2020 MA Strategic Reorganization Restructuring Program | Employee Severance
Restructuring Reserve [Roll Forward]
Cost incurred and adjustments	2
Cash payments and adjustments	(8)
Cost incurred to date	$ 20