Income Taxes(Components Of Deferred Income Taxes) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets relating to:
Retirement benefits	$ 362.9	$ 364.8
Accrued expenses	331.9	344.6
Insurance reserves	229.5	247.1
Net operating loss carryforwards	9.2	18.1
Bad debt reserves	119.6	154.8
State income tax	59.8	43.4
Deferred compensation	38.2	40.1
Investment basis difference	42.4	62.2
Other	110.5	68.4
Deferred Tax Assets, Gross	1,304.0	1,343.5
Deferred tax liabilities relating to:
Unrealized gains on securities	202.9	127.8
Trademarks and state Medicaid licenses	2,547.6	2,547.6
Customer, provider and hospital relationships	194.1	269.2
Internally developed software and other amortization differences	450.5	436.6
Retirement benefits	267.3	252.7
Debt discount	60.8	61.9
State deferred tax	106.0	36.4
Depreciation and amortization	54.1	44.2
Other	200.6	197.7
Total deferred tax liabilities	4,083.9	3,974.1
Net deferred tax liability	$ (2,779.9)	$ (2,630.6)