Restructuring - Changes in Restructuring Liability (Details) $ in Millions	Dec. 31, 2021 USD ($)
2018 Restructuring Program | Employee Termination Costs
Restructuring Cost and Reserve [Line Items]
Cumulative expense incurred through December 31, 2021	$ 55
2018 Restructuring Program | Contract Termination Costs
Restructuring Cost and Reserve [Line Items]
Cumulative expense incurred through December 31, 2021	48
2020 Real Estate Rationalization Restructuring Program | Employee Termination Costs
Restructuring Cost and Reserve [Line Items]
Cumulative expense incurred through December 31, 2021	0
2020 Real Estate Rationalization Restructuring Program | Contract Termination Costs
Restructuring Cost and Reserve [Line Items]
Cumulative expense incurred through December 31, 2021	36
2020 MA Strategic Reorganization Restructuring Program | Employee Termination Costs
Restructuring Cost and Reserve [Line Items]
Cumulative expense incurred through December 31, 2021	20
2020 MA Strategic Reorganization Restructuring Program | Contract Termination Costs
Restructuring Cost and Reserve [Line Items]
Cumulative expense incurred through December 31, 2021	$ 0