Fair Value Measurement - Summary of Quantitative Information about Partnership's Level III Inputs (Details) $ in Millions | Sep. 30, 2018USD ($)$ / shares | Dec. 31, 2017USD ($)$ / shares |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of liabilities | $ 4,777.6 | $ 4,306 |
Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of liabilities | 4,775.6 | 4,304.8 |
Investments of Consolidated Funds | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | 5,095.4 | 4,534.3 |
Investments in CLOs and other | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | 5,547.2 | 4,939.7 |
Discounted Cash Flow | Equity securities | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | | 5.7 |
Consensus Pricing | Equity securities | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | 6.5 | 2.2 |
Consensus Pricing | Bonds | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | 620.9 | 413.4 |
Consensus Pricing | Loans | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | 4,468 | 4,112.7 |
Counterparty Pricing | Other | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | | 0.3 |
Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | 54.6 | |
Fair value of liabilities | 212.4 | 176.4 |
Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | 397.2 | 357.2 |
Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of assets | | 48.2 |
Other | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of liabilities | 4,556.8 | 4,100.5 |
Other | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of liabilities | 5.4 | 26.9 |
Other | Contingent Consideration | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Fair value of liabilities | $ 1 | $ 1 |
Discount Rates | Minimum | Discounted Cash Flow | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Equity Securities, FV-NI, Measurement Input | | 0.10 |
Discount Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.09 | 0.08 |
Discount Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | | 0.01 |
Discount Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.09 | 0.08 |
Discount Rates | Maximum | Discounted Cash Flow | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Equity Securities, FV-NI, Measurement Input | | 0.10 |
Discount Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.12 | 0.11 |
Discount Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | | 0.09 |
Discount Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.12 | 0.11 |
Discount Rates | Weighted Average | Discounted Cash Flow | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Equity Securities, FV-NI, Measurement Input | | 0.10 |
Discount Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.10 | 0.10 |
Discount Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | | 0.03 |
Discount Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.11 | 0.09 |
Indicative Quotes | Minimum | Consensus Pricing | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Equity Securities, FV-NI, Measurement Input | $ / shares | 0 | 0 |
Indicative Quotes | Minimum | Consensus Pricing | Bonds | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0060 | 0.0044 |
Indicative Quotes | Minimum | Consensus Pricing | Loans | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0074 | 0.0064 |
Indicative Quotes | Minimum | Counterparty Pricing | Other | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | | 0.0009 |
Indicative Quotes | Minimum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.0074 | 0.0079 |
Indicative Quotes | Minimum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0091 | 0.0098 |
Indicative Quotes | Minimum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0052 | 0.0063 |
Indicative Quotes | Maximum | Consensus Pricing | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Equity Securities, FV-NI, Measurement Input | $ / shares | 97 | 33 |
Indicative Quotes | Maximum | Consensus Pricing | Bonds | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0107 | 0.0107 |
Indicative Quotes | Maximum | Consensus Pricing | Loans | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0103 | 0.0103 |
Indicative Quotes | Maximum | Counterparty Pricing | Other | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | | 0.0009 |
Indicative Quotes | Maximum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.0097 | 0.0093 |
Indicative Quotes | Maximum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0102 | 0.0104 |
Indicative Quotes | Maximum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0108 | 0.0097 |
Indicative Quotes | Weighted Average | Consensus Pricing | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Equity Securities, FV-NI, Measurement Input | $ / shares | 87 | 30 |
Indicative Quotes | Weighted Average | Consensus Pricing | Bonds | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0096 | 0.0098 |
Indicative Quotes | Weighted Average | Consensus Pricing | Loans | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0099 | 0.0100 |
Indicative Quotes | Weighted Average | Counterparty Pricing | Other | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | | 0.0009 |
Indicative Quotes | Weighted Average | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.0087 | 0.0086 |
Indicative Quotes | Weighted Average | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0100 | 0.0101 |
Indicative Quotes | Weighted Average | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0079 | 0.0081 |
Measurement Margin | Minimum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0085 | |
Measurement Margin | Maximum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0870 | |
Measurement Margin | Weighted Average | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.0162 | |
Default Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.01 | 0.01 |
Default Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.01 | 0.01 |
Default Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.01 | 0.01 |
Default Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.03 | 0.03 |
Default Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.03 | 0.03 |
Default Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.03 | 0.03 |
Default Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.02 | 0.02 |
Default Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.02 | 0.02 |
Default Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.02 | 0.02 |
Recovery Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.45 | 0.50 |
Recovery Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.45 | 0.50 |
Recovery Rates | Minimum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.45 | 0.50 |
Recovery Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.73 | 0.70 |
Recovery Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.73 | 0.70 |
Recovery Rates | Maximum | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.73 | 0.70 |
Recovery Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Debt instrument, measurement input | 0.60 | 0.60 |
Recovery Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Senior secured notes | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.57 | 0.60 |
Recovery Rates | Weighted Average | Discounted Cash Flow with Consensus Pricing | Subordinated notes and preferred shares | Level III | | |
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | | |
Alternative investment, measurement input | 0.57 | 0.60 |