Consolidated Investment Products - Schedule of Valuation Techniques and Significant Unobservable Inputs used in Level 3 Fair Value Measurements (Details) $ in Millions		Dec. 31, 2022 USD ($) $ / shares	Sep. 30, 2022 USD ($) $ / shares
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		$ 969.6	$ 613.5
CIPs [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		8,735.6	7,898.1
Fair Value, Recurring [Member] | CIPs [Member] | Equity and debt securities [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		2,132.4	1,685.7
Fair Value, Recurring [Member] | CIPs [Member] | Real Estate [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		358.0	268.6
Fair Value, Recurring [Member] | CIPs [Member] | Loans [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		6,245.2	5,943.8
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity and debt securities [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		555.8	555.8
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity and debt securities [Member] | Market pricing [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		$ 555.8	$ 555.8
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity and debt securities [Member] | Market pricing [Member] | Private sale pricing [Member] | Minimum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input | $ / shares		0.01	0.01
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity and debt securities [Member] | Market pricing [Member] | Private sale pricing [Member] | Maximum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input | $ / shares		1,000	558.45
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity and debt securities [Member] | Market pricing [Member] | Private sale pricing [Member] | Weighted Average [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input | $ / shares	[1]	39.93	33.31
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity and debt securities [Member] | Market comparable companies [Member] | Measurement Input, Discount for lack of liquidity | Minimum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.235	0.235
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity and debt securities [Member] | Market comparable companies [Member] | Measurement Input, Discount for lack of liquidity | Maximum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.251	0.251
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity and debt securities [Member] | Market comparable companies [Member] | Measurement Input, Discount for lack of liquidity | Weighted Average [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.249	0.249
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		$ 358.0	$ 268.6
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | Discounted cash flow [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		$ 358.0	$ 268.6
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | Discounted cash flow [Member] | Discount rate [Member] | Minimum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.055	0.045
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | Discounted cash flow [Member] | Discount rate [Member] | Maximum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.068	0.063
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | Discounted cash flow [Member] | Discount rate [Member] | Weighted Average [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input	[1]	0.062	0.051
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | Discounted cash flow [Member] | Exit Capitalization Rate [Member] | Minimum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.045	0.055
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | Discounted cash flow [Member] | Exit Capitalization Rate [Member] | Maximum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.063	0.068
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | Discounted cash flow [Member] | Exit Capitalization Rate [Member] | Weighted Average [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input	[1]	0.052	0.060
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value		$ 64.7	$ 239.4
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Discounted cash flow [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value			$ 60.4
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Discounted cash flow [Member] | Discount rate [Member] | Weighted Average [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input			9.9
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Market pricing [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value			$ 147.2
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Market pricing [Member] | Private sale pricing [Member] | Minimum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input | $ / shares			0.97
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Market pricing [Member] | Private sale pricing [Member] | Maximum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input | $ / shares			0.98
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Market pricing [Member] | Private sale pricing [Member] | Weighted Average [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input | $ / shares			0.98
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Yield capitalization [Member]
Schedule Of Consolidated Investment Products [Line Items]
Total investments, at fair value			$ 31.9
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Yield capitalization [Member] | Measurement Input, Credit Spread | Minimum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.060
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Yield capitalization [Member] | Measurement Input, Credit Spread | Maximum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.073
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Yield capitalization [Member] | Measurement Input, Credit Spread | Weighted Average [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.065	6.3
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Yield capitalization [Member] | Measurement Input, Loan-to-value ratio | Minimum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.646	0.791
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Yield capitalization [Member] | Measurement Input, Loan-to-value ratio | Maximum [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.772	0.881
Fair Value, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Yield capitalization [Member] | Measurement Input, Loan-to-value ratio | Weighted Average [Member]
Schedule Of Consolidated Investment Products [Line Items]
Investments, measurement input		0.702	0.831

[1] Based on the relative fair value of the instruments.