Income Taxes(Components Of Deferred Income Taxes) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets relating to:
Retirement benefits	$ 364.8	$ 357.7
Accrued expenses	344.6	329.9
Insurance reserves	247.1	209.7
Net operating loss carryforwards	18.1	14.8
Bad debt reserves	154.8	132.9
State income tax	43.4	40.6
Deferred compensation	40.1	46.6
Investment basis difference	62.2	88.2
Other	68.4	34.2
Total deferred tax assets	1,343.5	1,254.6
Valuation allowance	0.0	(2.6)
Total deferred tax assets, net of valuation allowance	1,343.5	1,252.0
Deferred tax liabilities relating to:
Unrealized gains on securities	127.8	331.4
Trademarks and state Medicaid licenses	2,547.6	2,444.3
Customer, provider and hospital relationships	269.2	308.6
Internally developed software and other amortization differences	436.6	403.6
Retirement benefits	252.7	241.1
Debt discount	61.9	184.0
State deferred tax	36.4	49.1
Depreciation and amortization	44.2	29.6
Other	197.7	205.9
Total deferred tax liabilities	3,974.1	4,197.6
Net deferred tax liability	$ (2,630.6)	$ (2,945.6)