Fair Value Measurements - Summary of the Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended |
Mar. 31, 2023 | Dec. 31, 2022 |
Asset of BSIF and consolidated Funds | | |
Total fair value assets | $ 52.7 | $ 50.3 |
Derivative Liability, Statement of Financial Position [Extensible Enumeration] | Derivative liabilities at fair value | Derivative liabilities at fair value |
Total fair value liabilities | $ (2.6) | $ (2.2) |
Investments in unconsolidated funds | | |
Asset of BSIF and consolidated Funds | | |
Uncategorized | $ 4.3 | 4.2 |
Minimum | Real estate investment funds | | |
Asset of BSIF and consolidated Funds | | |
Term over which the underlying assets are expected to be liquidated by the investees | 1 year | |
Maximum | Real estate investment funds | | |
Asset of BSIF and consolidated Funds | | |
Term over which the underlying assets are expected to be liquidated by the investees | 2 years | |
Consolidated Entity Excluding Consolidated Funds | | |
Asset of BSIF and consolidated Funds | | |
Derivatives | $ 2.8 | 1.9 |
Derivative asset Consolidated Funds total | 2.8 | 1.9 |
Consolidated Funds total | 49.9 | 48.4 |
Derivative Liability | (2.6) | (2.2) |
Consolidated Funds total | (2.6) | (2.2) |
Consolidated Entity Excluding Consolidated Funds | Investments in separate accounts | | |
Asset of BSIF and consolidated Funds | | |
Investments in separate accounts | 4.4 | 4.2 |
Consolidated Entity Excluding Consolidated Funds | Investments related to long-term incentive compensation plans | | |
Asset of BSIF and consolidated Funds | | |
Investments related to long-term incentive compensation plans | 41.2 | 40 |
Investments in unconsolidated Funds | 41.2 | 40 |
Consolidated Entity Excluding Consolidated Funds | Investments in unconsolidated funds | | |
Asset of BSIF and consolidated Funds | | |
Investments in unconsolidated Funds | 4.3 | 4.2 |
Uncategorized | 4.3 | 4.2 |
Consolidated Entity Excluding Consolidated Funds | Investment Funds Subject to Longer Redemption Restrictions | | |
Asset of BSIF and consolidated Funds | | |
Uncategorized | 4.2 | 4.1 |
Quoted prices in active markets (Level I) | | |
Asset of BSIF and consolidated Funds | | |
Total fair value assets | 45.9 | 44.5 |
Total fair value liabilities | (0.3) | (0.2) |
Quoted prices in active markets (Level I) | Consolidated Entity Excluding Consolidated Funds | | |
Asset of BSIF and consolidated Funds | | |
Derivatives | 0.3 | 0.3 |
Derivative asset Consolidated Funds total | 0.3 | 0.3 |
Consolidated Funds total | 45.6 | 44.2 |
Uncategorized | 4.3 | 4.2 |
Derivative Liability | (0.3) | (0.2) |
Consolidated Funds total | $ (0.3) | $ (0.2) |
Investment in equity securities | 100% | 100% |
Quoted prices in active markets (Level I) | Consolidated Entity Excluding Consolidated Funds | Investments in separate accounts | | |
Asset of BSIF and consolidated Funds | | |
Investments in separate accounts | $ 4.4 | $ 4.2 |
Quoted prices in active markets (Level I) | Consolidated Entity Excluding Consolidated Funds | Investments related to long-term incentive compensation plans | | |
Asset of BSIF and consolidated Funds | | |
Investments related to long-term incentive compensation plans | 41.2 | 40 |
Quoted prices in active markets (Level I) | Consolidated Entity Excluding Consolidated Funds | Investments in unconsolidated funds | | |
Asset of BSIF and consolidated Funds | | |
Investments in unconsolidated Funds | 0 | 0 |
Significant other observable inputs (Level II) | | |
Asset of BSIF and consolidated Funds | | |
Total fair value assets | 2.5 | 1.6 |
Total fair value liabilities | (2.3) | (2) |
Significant other observable inputs (Level II) | Consolidated Entity Excluding Consolidated Funds | | |
Asset of BSIF and consolidated Funds | | |
Derivatives | 2.5 | 1.6 |
Derivative asset Consolidated Funds total | 2.5 | 1.6 |
Consolidated Funds total | 0 | 0 |
Derivative Liability | (2.3) | (2) |
Consolidated Funds total | (2.3) | (2) |
Significant other observable inputs (Level II) | Consolidated Entity Excluding Consolidated Funds | Investments in separate accounts | | |
Asset of BSIF and consolidated Funds | | |
Investments in separate accounts | 0 | 0 |
Significant other observable inputs (Level II) | Consolidated Entity Excluding Consolidated Funds | Investments related to long-term incentive compensation plans | | |
Asset of BSIF and consolidated Funds | | |
Investments related to long-term incentive compensation plans | 0 | 0 |
Significant other observable inputs (Level II) | Consolidated Entity Excluding Consolidated Funds | Investments in unconsolidated funds | | |
Asset of BSIF and consolidated Funds | | |
Investments in unconsolidated Funds | 0 | 0 |
Significant unobservable inputs (Level III) | | |
Asset of BSIF and consolidated Funds | | |
Total fair value assets | 0 | 0 |
Total fair value liabilities | 0 | 0 |
Significant unobservable inputs (Level III) | Consolidated Entity Excluding Consolidated Funds | | |
Asset of BSIF and consolidated Funds | | |
Derivatives | 0 | 0 |
Derivative asset Consolidated Funds total | 0 | 0 |
Consolidated Funds total | 0 | 0 |
Derivative Liability | 0 | 0 |
Consolidated Funds total | 0 | 0 |
Significant unobservable inputs (Level III) | Consolidated Entity Excluding Consolidated Funds | Investments in separate accounts | | |
Asset of BSIF and consolidated Funds | | |
Investments in separate accounts | 0 | 0 |
Significant unobservable inputs (Level III) | Consolidated Entity Excluding Consolidated Funds | Investments related to long-term incentive compensation plans | | |
Asset of BSIF and consolidated Funds | | |
Investments related to long-term incentive compensation plans | 0 | 0 |
Significant unobservable inputs (Level III) | Consolidated Entity Excluding Consolidated Funds | Investments in unconsolidated funds | | |
Asset of BSIF and consolidated Funds | | |
Investments in unconsolidated Funds | $ 0 | $ 0 |