Business Optimization Initiatives (Employee Termination Costs) (Details) - Employee Severance [Member] $ in Millions	6 Months Ended
	Jun. 30, 2021 USD ($)
Business Optimization Initiatives [Line Items]
Liability for employee terminations costs, beginning	$ 187
Payments	(26)
Liability for employee terminations costs, ending	161
IngenioRx Segment [Member]
Business Optimization Initiatives [Line Items]
Liability for employee terminations costs, beginning	1
Payments	0
Liability for employee terminations costs, ending	1
Other Segment [Member]
Business Optimization Initiatives [Line Items]
Liability for employee terminations costs, beginning	6
Payments	(1)
Liability for employee terminations costs, ending	5
Government Business Segment [Member]
Business Optimization Initiatives [Line Items]
Liability for employee terminations costs, beginning	88
Payments	(13)
Liability for employee terminations costs, ending	75
Commercial Specialty Business Segment [Member]
Business Optimization Initiatives [Line Items]
Liability for employee terminations costs, beginning	92
Payments	(12)
Liability for employee terminations costs, ending	$ 80