Consolidated Investment Products - Schedule of Valuation Techniques and Significant Unobservable Inputs used in Level 3 Fair Value Measurements (Details) $ in Millions | Jun. 30, 2019USD ($)$ / shares | Sep. 30, 2018USD ($)$ / shares |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 619.4 | | $ 551.6 |
CIPs [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | 2,351.1 | | 2,109.4 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Equity securities [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | 867.5 | | 739 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Debt Securities [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | 1,429.6 | | 1,338.1 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Loans [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | 24.9 | | 32.3 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Real Estate [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | 29.1 | | |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | 267.6 | | 199.7 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Market comparable companies [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 128.5 | | $ 171.9 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Market comparable companies [Member] | EBITDA multiple [Member] | Minimum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 4.7 | | 5 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Market comparable companies [Member] | EBITDA multiple [Member] | Maximum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 13.6 | | 13.6 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Market comparable companies [Member] | EBITDA multiple [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 9.7 | [1] | 9.3 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Discounted cash flow [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 117.1 | | $ 27.8 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Discounted cash flow [Member] | Discount rate [Member] | Minimum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.060 | | 0.080 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Discounted cash flow [Member] | Discount rate [Member] | Maximum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.182 | | 0.165 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Discounted cash flow [Member] | Discount rate [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.127 | [1] | 0.141 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Market Pricing [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 22 | | |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Market Pricing [Member] | Private sale pricing [Member] | Minimum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | $ / shares | | 0.25 | | |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Market Pricing [Member] | Private sale pricing [Member] | Maximum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | $ / shares | | 3.38 | | |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Equity securities [Member] | Market Pricing [Member] | Private sale pricing [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | $ / shares | [1] | 1.50 | | |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 140.6 | | $ 118 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Market comparable companies [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 28.7 | | $ 33.9 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Market comparable companies [Member] | EBITDA multiple [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 12.3 | [1] | 20.9 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Market comparable companies [Member] | Price-to-earnings ratio [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 10 | [1] | 10 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Discounted cash flow [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 111.9 | | $ 78.7 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Discounted cash flow [Member] | Discount rate [Member] | Minimum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.055 | | 0.070 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Discounted cash flow [Member] | Discount rate [Member] | Maximum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.230 | | 0.148 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Discounted cash flow [Member] | Discount rate [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.104 | [1] | 0.108 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Market Pricing [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | | | $ 5.4 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Debt Securities [Member] | Market Pricing [Member] | Private sale pricing [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | $ / shares | | | | 0.42 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 24.9 | | $ 32.3 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Discounted cash flow [Member] | Loss-adjusted discount rate [Member] | Minimum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.030 | | 0.030 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Discounted cash flow [Member] | Loss-adjusted discount rate [Member] | Maximum [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.253 | | 0.227 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Loans [Member] | Discounted cash flow [Member] | Loss-adjusted discount rate [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | | 0.132 | [1] | 0.120 |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, at fair value | | $ 29.1 | | |
Fair Value, Measurements, Recurring [Member] | CIPs [Member] | Level 3 [Member] | Real Estate [Member] | Yield capitalization [Member] | Equivalent yield [Member] | Weighted Average [Member] | | | | |
Schedule Of Consolidated Investment Products [Line Items] | | | | |
Investments, measurement input | [1] | 0.050 | | |
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[1] | Based on the relative fair value of the instruments. | |