Business Optimization Initiatives (Employee Termination Costs) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	$ 653
Employee Termination [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	197
Business optimization initiatives, payments	(10)
Business optimization initiatives, cost	187
IngenioRx Segment [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	4
IngenioRx Segment [Member] | Employee Termination [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	1
Business optimization initiatives, payments	0
Business optimization initiatives, cost	1
Other Segment [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	133
Other Segment [Member] | Employee Termination [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	8
Business optimization initiatives, payments	(2)
Business optimization initiatives, cost	6
Government Business [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	205
Government Business [Member] | Employee Termination [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	92
Business optimization initiatives, payments	(4)
Business optimization initiatives, cost	88
Commercial and Specialty Business [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	311
Commercial and Specialty Business [Member] | Employee Termination [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	96
Business optimization initiatives, payments	(4)
Business optimization initiatives, cost	$ 92