Consolidated Investment Products - Schedule of Investments measured at NAV (Details) - USD ($) $ in Millions |
6 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Mar. 31, 2024 |
Sep. 30, 2023 |
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| Schedule Of Consolidated Investment Products [Line Items] | |||||||||||
| Unfunded commitments | $ 43.1 | $ 43.1 | |||||||||
| Nonredeemable investments with known liquidation periods | |||||||||||
| Schedule Of Consolidated Investment Products [Line Items] | |||||||||||
| Alternative Investment | [1] | $ 36.7 | $ 32.1 | ||||||||
| Liquidation weighted-average period | 2 years 7 months 6 days | 2 years 10 months 24 days | |||||||||
| Nonredeemable investments with unknown liquidation periods | |||||||||||
| Schedule Of Consolidated Investment Products [Line Items] | |||||||||||
| Alternative Investment | [1] | $ 16.4 | $ 17.4 | ||||||||
| Redeemable Funds | |||||||||||
| Schedule Of Consolidated Investment Products [Line Items] | |||||||||||
| Alternative Investment | [2] | 53.9 | 50.2 | ||||||||
| CIPs [Member] | Nonredeemable investments with unknown liquidation periods | |||||||||||
| Schedule Of Consolidated Investment Products [Line Items] | |||||||||||
| Alternative Investment | 23.9 | 21.8 | [3] | ||||||||
| CIPs [Member] | Redeemable Funds | |||||||||||
| Schedule Of Consolidated Investment Products [Line Items] | |||||||||||
| Alternative Investment | [4] | $ 136.3 | $ 132.2 | ||||||||
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