Fair Value Of Assets And Liabilities (Tri-Level Hierarchy, Carrying Value) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	$ 188.5	$ 233.2
Assets held for policyholders	6,620.4	6,051.5
Put option contracts	14.1	1.4
Total	7,547.9	7,072.1
Total	(90.8)	(86.4)
Foreign time deposits	15.0	24.7
Equity method investments	286.0	352.8
Cost method investments	5.7	5.7
Corporate Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
UIT-related financial instruments sold, not yet purchased	(1.5)	(2.5)
Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	(89.3)	(83.9)
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	328.1	383.3
Seed Money [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	173.7	225.9
Trading investments	193.1	191.2
Collateralized Loan Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	11.5	1.4
Other Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	3.3	5.9
Deferred Compensation Arrangements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	168.5	158.8
Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	31.4	48.1
Corporate Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	1.7	1.8
UIT-Related Equity And Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.3	1.5
Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	1.8	1.3
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for policyholders	6,620.4	6,051.5
Put option contracts	0.0	0.0
Total	7,517.2	7,062.1
Total	(1.5)	(2.5)
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
UIT-related financial instruments sold, not yet purchased	(1.5)	(2.5)
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	328.1	383.3
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Seed Money [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	173.7	225.9
Trading investments	193.1	191.2
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Collateralized Loan Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	0.0	0.0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Deferred Compensation Arrangements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	168.5	158.8
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	31.4	48.1
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	1.7	1.8
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | UIT-Related Equity And Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.3	1.5
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for policyholders	0.0	0.0
Put option contracts	14.1	1.4
Total	15.9	2.7
Total	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Corporate Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
UIT-related financial instruments sold, not yet purchased	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Seed Money [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	0.0	0.0
Trading investments	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Collateralized Loan Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Other Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Deferred Compensation Arrangements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Corporate Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | UIT-Related Equity And Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Other Observable Inputs (Level 2) [Member] | Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	1.8	1.3
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held for policyholders	0.0	0.0
Put option contracts	0.0	0.0
Total	14.8	7.3
Total	(89.3)	(83.9)
Significant Unobservable Inputs (Level 3) [Member] | Corporate Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
UIT-related financial instruments sold, not yet purchased	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, Fair Value Disclosure	(89.3)	(83.9)
Significant Unobservable Inputs (Level 3) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Seed Money [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	0.0	0.0
Trading investments	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Collateralized Loan Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	11.5	1.4
Significant Unobservable Inputs (Level 3) [Member] | Other Debt Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	3.3	5.9
Significant Unobservable Inputs (Level 3) [Member] | Deferred Compensation Arrangements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Corporate Equities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | UIT-Related Equity And Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	0.0	0.0
Significant Unobservable Inputs (Level 3) [Member] | Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading investments	$ 0.0	$ 0.0