CONSOLIDATED INVESTMENT PRODUCTS - Fair Value Hierarchy Levels of Investments Held and Notes Issued by Consolidated Investment Products (Details) - USD ($) $ in Millions | Mar. 31, 2024 | Dec. 31, 2023 |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Total assets at fair value | $ 8,902.2 | $ 8,765.9 |
Consolidated | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Real estate investments | 445.5 | 463.6 |
Total assets at fair value | 8,902.2 | 8,765.9 |
Consolidated | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Real estate investments | 0 | 0 |
Total assets at fair value | 42.2 | 106.5 |
Consolidated | Significant Other Observable Inputs (Level 2) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Real estate investments | 0 | 0 |
Total assets at fair value | 6,887.7 | 6,944.5 |
Consolidated | Significant Unobservable Inputs (Level 3) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Real estate investments | 0 | 0 |
Total assets at fair value | 1,114.2 | 825.8 |
Consolidated | Investments Measured at NAV as a practical expedient | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Real estate investments | 445.5 | 463.6 |
Total assets at fair value | 858.1 | 889.1 |
Consolidated | Bank loans | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 7,133.8 | 6,837.2 |
Consolidated | Bank loans | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 0 | 0 |
Consolidated | Bank loans | Significant Other Observable Inputs (Level 2) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 6,143.3 | 6,140.1 |
Consolidated | Bank loans | Significant Unobservable Inputs (Level 3) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 990.5 | 697.1 |
Consolidated | Bank loans | Investments Measured at NAV as a practical expedient | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 0 | 0 |
Consolidated | Bonds | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 624.5 | 669.8 |
Consolidated | Bonds | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 11.9 | 13.3 |
Consolidated | Bonds | Significant Other Observable Inputs (Level 2) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 612.3 | 656.2 |
Consolidated | Bonds | Significant Unobservable Inputs (Level 3) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 0.3 | 0.3 |
Consolidated | Bonds | Investments Measured at NAV as a practical expedient | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 0 | 0 |
Consolidated | Equity securities, Equity and fixed income mutual funds | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 172.9 | 231.9 |
Equity and fixed income mutual funds, and investments in other private equity funds | 112.9 | 137.9 |
Consolidated | Equity securities, Equity and fixed income mutual funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 30.1 | 85.2 |
Equity and fixed income mutual funds, and investments in other private equity funds | 0.2 | 8 |
Consolidated | Equity securities, Equity and fixed income mutual funds | Significant Other Observable Inputs (Level 2) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 19.4 | 18.3 |
Equity and fixed income mutual funds, and investments in other private equity funds | 112.7 | 129.9 |
Consolidated | Equity securities, Equity and fixed income mutual funds | Significant Unobservable Inputs (Level 3) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 123.4 | 128.4 |
Equity and fixed income mutual funds, and investments in other private equity funds | 0 | 0 |
Consolidated | Equity securities, Equity and fixed income mutual funds | Investments Measured at NAV as a practical expedient | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Bank loan, bonds and equity securities | 0 | 0 |
Equity and fixed income mutual funds, and investments in other private equity funds | 0 | 0 |
Consolidated | Investments in other private equity funds | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Equity and fixed income mutual funds, and investments in other private equity funds | 412.6 | 425.5 |
Consolidated | Investments in other private equity funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Equity and fixed income mutual funds, and investments in other private equity funds | 0 | 0 |
Consolidated | Investments in other private equity funds | Significant Other Observable Inputs (Level 2) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Equity and fixed income mutual funds, and investments in other private equity funds | 0 | 0 |
Consolidated | Investments in other private equity funds | Significant Unobservable Inputs (Level 3) | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Equity and fixed income mutual funds, and investments in other private equity funds | 0 | 0 |
Consolidated | Investments in other private equity funds | Investments Measured at NAV as a practical expedient | | |
Segment Reporting, Other Significant Reconciling Items [Line Items] | | |
Equity and fixed income mutual funds, and investments in other private equity funds | $ 412.6 | $ 425.5 |