Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable By Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period			$ 7,892.6	$ 7,569.8
Ceded medical claims payable, beginning of period			(539.1)	(645.6)
Net medical claims payable, beginning of period			7,353.5	6,924.2
Current period net incurred medical claims			35,686.5	32,452.2
Prior periods redundancies			(951.0)	(726.3)
Total net incurred medical claims	$ 17,561.6	$ 16,500.7	34,735.5	31,725.9
Net payments attributable to current period medical claims			28,540.4	26,197.1
Net payments attributable to prior periods medical claims			6,070.9	5,541.4
Total net payments			34,611.3	31,738.5
Net medical claims payable, end of period	7,477.7	6,911.6	7,477.7	6,911.6
Ceded medical claims payable, end of period	491.8	587.0	491.8	587.0
Gross medical claims payable, end of period	7,969.5	7,498.6	7,969.5	7,498.6
Government Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period			4,625.6	4,173.7
Ceded medical claims payable, beginning of period			(17.8)	(9.9)
Net medical claims payable, beginning of period			4,607.8	4,163.8
Current period net incurred medical claims			21,263.1	19,056.0
Prior periods redundancies			(542.1)	(304.4)
Total net incurred medical claims	10,297.2	9,607.4	20,721.0	18,751.6
Net payments attributable to current period medical claims			17,045.2	14,979.2
Net payments attributable to prior periods medical claims			3,699.8	3,538.1
Total net payments			20,745.0	18,517.3
Net medical claims payable, end of period	4,583.8	4,398.1	4,583.8	4,398.1
Ceded medical claims payable, end of period	22.3	15.8	22.3	15.8
Gross medical claims payable, end of period	4,606.1	4,413.9	4,606.1	4,413.9
Commercial Specialty Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period			3,267.0	3,396.1
Ceded medical claims payable, beginning of period			(521.3)	(635.7)
Net medical claims payable, beginning of period			2,745.7	2,760.4
Current period net incurred medical claims			14,423.4	13,396.2
Prior periods redundancies			(408.9)	(421.9)
Total net incurred medical claims	7,264.4	6,893.3	14,014.5	12,974.3
Net payments attributable to current period medical claims			11,495.2	11,217.9
Net payments attributable to prior periods medical claims			2,371.1	2,003.3
Total net payments			13,866.3	13,221.2
Net medical claims payable, end of period	2,893.9	2,513.5	2,893.9	2,513.5
Ceded medical claims payable, end of period	469.5	571.2	469.5	571.2
Gross medical claims payable, end of period	$ 3,363.4	$ 3,084.7	$ 3,363.4	$ 3,084.7