Reorganization and Business Transformation - Costs Incurred For Reorganization Plan (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
2020 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring reserve. beginning balance	$ 18
Expense accruals	7
Cash payments	(17)
Restructuring reserve. ending balance	8
Voluntary Separation Program
Restructuring Cost and Reserve [Line Items]
Restructuring reserve. beginning balance	16
Expense accruals	2
Cash payments	(11)
Restructuring reserve. ending balance	7
Workforce Reduction and Real Estate Rationalization Measures | Employee severance and other employee-related costs
Restructuring Cost and Reserve [Line Items]
Restructuring reserve. beginning balance	2
Expense accruals	3
Cash payments	(4)
Restructuring reserve. ending balance	1
Workforce Reduction and Real Estate Rationalization Measures | Facilities lease related costs, outside service, legal and other associated costs
Restructuring Cost and Reserve [Line Items]
Restructuring reserve. beginning balance	0
Expense accruals	2
Cash payments	(2)
Restructuring reserve. ending balance	$ 0