Fair Value Measurements (Changes in the Balances of Level 3 Financial Assets) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Available-For-Sale Investments [Member]	Sep. 30, 2011 Available-For-Sale Investments [Member]	Sep. 30, 2012 Available-For-Sale Investments [Member]	Sep. 30, 2011 Available-For-Sale Investments [Member]	Sep. 30, 2012 Embedded Contractual Derivative [Member]	Sep. 30, 2011 Embedded Contractual Derivative [Member]	Sep. 30, 2012 Embedded Contractual Derivative [Member]	Sep. 30, 2011 Embedded Contractual Derivative [Member]	Sep. 30, 2012 Divested Operations and Services [Member]	Sep. 30, 2012 Divested Operations and Services [Member]	Apr. 02, 2012 Divested Operations and Services [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	$ 15.2	$ 10.7	$ 5.5	$ 9.9	$ 0.2	$ 9.9	$ 0.2	$ 9.9	$ 15.0	$ 0.8	$ 5.3	$ 0
Transfers into Level 3	0	0	0	0	0	0	0	0	0	0	0	0
Transfers out of Level 3	0	0	0	0	0	0	0	0	0	0	0	0
Total gains or losses for the period
Realized in net income	(7.8)	(1.7)	1.9	(0.9)	0	(2.4)	0	(2.4)	(7.8)	0.7	1.9	1.5
Unrealized in accumulated other comprehensive income	0	0	0	0	0	0	0	0	0	0	0	0
Purchases, issues, sales and settlements
Purchases/additions	0	0	0	0	0	0	0	0	0	0	0	0
Issues	0	0	0	0	0	0	0	0	0	0	0	0
Sales	0	(7.3)	0	(7.3)	0	(7.3)	0	(7.3)	0	0	0	0
Settlements	0	0	0	0	0	0	0	0	0	0	0	0
Closing balance	7.4	1.7	7.4	1.7	0.2	0.2	0.2	0.2	7.2	1.5	7.2	1.5
Change in unrealized gains (losses) included in net income for assets held at the end of the reporting period	0	0	0	0	0	0	0	0	0	0	0	0
Changes in Level 3 Financial Assets and Liabilities, Non-Recurring Basis
Beginning balance: goodwill of discontinued operation	0		40.0
Goodwill allocated to Medicare PDP business sold	0		(40.0)
Ending balance: goodwill of discontinued operation	0		0
Beginning balance, Deferred revenue related to transition-related services provided in connection with Medicare PDP business sale													8.0	0	12.0
Deferred revenue, realized in net income													(4.0)	(8.0)
Deferred revenue, Additions													0	12.0
Ending balance, Deferred revenue related to transition-related services provided in connection with Medicare PDP business sale													$ 4.0	$ 4.0	$ 12.0

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Unrealized Gains (Losses) Still Held.

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Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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Amount of deferred revenue recognized for transactions arising during the current reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an Entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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Amount of previously reported deferred or unearned revenue that was recognized as revenue during the period. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

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For the disposal group, including a component of the entity (discontinued operation), carrying amount of goodwill (adjusted for any amortization recognized prior to adoption of FAS 142 and impairment charges).

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Amount of gain (loss) recognized in earnings, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

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Amount of gain (loss) recognized in other comprehensive income, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

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Issues that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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Sales that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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Transfers into assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

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Transfers out of assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

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This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

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Write-off of the carrying amount of goodwill associated with all or a portion of a reporting unit that is sold in the period.

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