Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of beginning and ending balances for medical claims payable
Gross medical claims payable, beginning of year	$ 6,861.2	$ 6,127.2	$ 6,174.5
Ceded medical claims payable, beginning of year	(767.4)	(23.4)	(27.2)
Net medical claims payable, beginning of year	6,093.8	6,103.8	6,147.3
Business combinations and purchase adjustments	121.8	0.0	0.0
Net incurred medical claims in current year	60,708.4	56,305.8	55,894.3
Net incurred medical claims in prior years redundancies	(800.2)	(541.9)	(599.1)
Total net incurred medical claims	59,908.2	55,763.9	55,295.2
Net payments attributable to current year medical claims	54,067.7	50,353.9	49,887.2
Net payments attributable to prior years medical claims	5,131.9	5,420.0	5,451.5
Total net payments	59,199.6	55,773.9	55,338.7
Net medical claims payable, end of year	6,924.2	6,093.8	6,103.8
Ceded medical claims payable, end of year	645.6	767.4	23.4
Gross medical claims payable, end of year	$ 7,569.8	$ 6,861.2	$ 6,127.2