Fair Value Measurements (Changes in the Balances of Level 3 Financial Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 5.5	$ 9.9
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Settlements	0	0
Total Gains And Losses
Realized in net income	5.9	2.9
Unrealized in accumulated other comprehensive income	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Issuances	0	0
Sales	0	(7.3)
Ending balance	11.4	5.5
Change in unrealized gains (losses) included in net income related to assets still held at the end of the reporting period	0	0
Changes in Level 3 Financial Assets and Liabilities, Non-Recurring Basis [Abstract]
Beginning balance: goodwill allocated to Medicare PDP business sold	0
Goodwill, Allocation Adjustment	40.0
Goodwill allocated to business sold	40.0
Ending balance: goodwill allocated to Medicare PDP business sold	0	0
Beginning balance: Deferred revenue	0
Deferred revenue, realized in net income	(12.0)
Additions	12.0
Ending balance: Deferred revenue	0	0
Nonrecurring [Member]
Changes in Level 3 Financial Assets and Liabilities, Non-Recurring Basis [Abstract]
Lease impairment obligation, beginning balance	0
Liabilities, Fair Value Adjustment	7.4
Lease impairment obligation, ending balance	7.4
Available-For-Sale Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	0.2	9.9
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Settlements	0	0
Total Gains And Losses
Realized in net income	0	(2.4)
Unrealized in accumulated other comprehensive income	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Issuances	0	0
Sales	0	(7.3)
Ending balance	0.2	0.2
Change in unrealized gains (losses) included in net income related to assets still held at the end of the reporting period	0	0
Embedded Contractual Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	5.3	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Settlements	0	0
Total Gains And Losses
Realized in net income	5.9	5.3
Unrealized in accumulated other comprehensive income	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Issuances	0	0
Sales	0	0
Ending balance	11.2	5.3
Change in unrealized gains (losses) included in net income related to assets still held at the end of the reporting period	$ 0	$ 0