Fair Value Of Assets And Liabilities (Tri-Level Hierarchy, Carrying Value) (Details) - USD ($) $ in Millions | Jun. 30, 2018 | Dec. 31, 2017 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | $ 1 | $ 85.2 |
Equity investments | 383.6 | 346.6 |
Assets held for policyholders | 12,199.6 | 12,444.5 |
Total | 13,056.7 | 13,682.5 |
Total | (50.1) | (57.4) |
Foreign time deposits | | 28.6 |
Equity Method Investments | 315.2 | 277.3 |
Liability [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | (50.1) | (57.4) |
Money Market Funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 472.5 | 875.5 |
Seed money | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 274.3 | 243 |
Deferred Compensation Arrangements [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 93.6 | 92.3 |
Equity Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | | 11.3 |
CLOs | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | 1 | 6 |
Other debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | | 9.9 |
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 | 12,199.6 | 12,444.5 |
Total | 13,055.7 | 13,666.6 |
Total | 0 | 0 |
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 |
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 | 472.5 | 875.5 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Seed money | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 274.3 | 243 |
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] | | |
Equity investments | 93.6 | 92.3 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 15.7 | 11.3 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | CLOs | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | 0 | 0 |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | | 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 |
Total | 1 | 6 |
Total | 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 |
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 |
Significant Other Observable Inputs (Level 2) [Member] | Seed money | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 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] | | |
Equity investments | 0 | 0 |
Significant Other Observable Inputs (Level 2) [Member] | Equity Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 0 | 0 |
Significant Other Observable Inputs (Level 2) [Member] | CLOs | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | 1 | 6 |
Significant Other Observable Inputs (Level 2) [Member] | Other debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | | 0 |
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 |
Total | 0 | 9.9 |
Total | (50.1) | (57.4) |
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 | (50.1) | (57.4) |
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 |
Significant Unobservable Inputs (Level 3) [Member] | Seed money | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Deferred Compensation Arrangements [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | CLOs | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | 0 | 0 |
Significant Unobservable Inputs (Level 3) [Member] | Other debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Available for sale investments | | $ 9.9 |
Common Stock [Member] | Equity Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity investments | $ 15.7 | |