Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of beginning and ending balances for medical claims payable
Gross medical claims payable, beginning of year	$ 6,127.2	$ 6,174.5	$ 5,489.0
Ceded medical claims payable, beginning of year	(23.4)	(27.2)	(16.4)
Net medical claims payable, beginning of year	6,103.8	6,147.3	5,472.6
Business combinations and purchase adjustments	0	0	804.4
Net incurred medical claims in current year	56,305.8	55,894.3	48,080.1
Net incurred medical claims in prior years redundancies	(541.9)	(599.1)	(513.6)
Total net incurred medical claims	55,763.9	55,295.2	47,566.5
Net payments attributable to current year medical claims	50,353.9	49,887.2	42,832.4
Net payments attributable to prior years medical claims	5,420.0	5,451.5	4,863.8
Total net payments	55,773.9	55,338.7	47,696.2
Net medical claims payable, end of year	6,093.8	6,103.8	6,147.3
Ceded medical claims payable, end of year	767.4	23.4	27.2
Gross medical claims payable, end of year	$ 6,861.2	$ 6,127.2	$ 6,174.5