Fair Value Measurements - Schedule of investments measured at NAV (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Dec. 31, 2022	Sep. 30, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unfunded commitments		$ 51.4	$ 51.4
Nonredeemable investments with unknown liquidation periods
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investment	[1]	21.9	29.4
Nonredeemable investments with known liquidation periods
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investment	[1]	$ 31.7	$ 32.8
Liquidation weighted-average period		3 years 6 months	3 years 4 months 24 days
Redeemable Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Alternative Investment	[2]	$ 48.3	$ 23.8

[1] The investments are expected to be returned through distributions over the life of the funds as a result of liquidations of the funds’ underlying assets. Investments with known liquidation periods have an expected weighted-average life of 3.5 years and 3.4 years at December 31, 2022 and September 30, 2022.

[2] Investments are redeemable on a semi-monthly, monthly and quarterly basis.