Business Optimization Initiatives (Narrative) (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
Property and Equipment Impairment and Abandonment [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	198
Operating Lease Impairment and Abandonment [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	258
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
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
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
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