Fair Value Measurements - Summary of the Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions | | | 9 Months Ended |
Sep. 30, 2022 | Dec. 31, 2021 | Sep. 30, 2022 |
Asset of BSIF and consolidated Funds | | | |
Total fair value assets | $ 45.9 | $ 54.5 | $ 45.9 |
Investments in unconsolidated funds | | | |
Asset of BSIF and consolidated Funds | | | |
Uncategorized | 4 | 4.9 | $ 4 |
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 |
Consolidated Entity Excluding Consolidated Funds | | | |
Asset of BSIF and consolidated Funds | | | |
Uncategorized | 4 | | $ 4 |
Consolidated Entity Excluding Consolidated Funds | Investments in separate accounts | | | |
Asset of BSIF and consolidated Funds | | | |
Investments in separate accounts | 3.8 | 4.6 | 3.8 |
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 | 38.1 | 45 | 38.1 |
Investments in unconsolidated Funds | 38.1 | 45 | 38.1 |
Consolidated Entity Excluding Consolidated Funds | Investments in unconsolidated funds | | | |
Asset of BSIF and consolidated Funds | | | |
Uncategorized | 4 | 4.9 | 4 |
Investments in unconsolidated Funds | 4 | 4.9 | 4 |
Consolidated Entity Excluding Consolidated Funds | Investment Funds Subject to Longer Redemption Restrictions | | | |
Asset of BSIF and consolidated Funds | | | |
Uncategorized | 3.9 | 4.8 | 3.9 |
Quoted prices in active markets (Level I) | | | |
Asset of BSIF and consolidated Funds | | | |
Total fair value assets | $ 41.9 | $ 49.6 | 41.9 |
Quoted prices in active markets (Level I) | Consolidated Entity Excluding Consolidated Funds | | | |
Asset of BSIF and consolidated Funds | | | |
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 | $ 3.8 | $ 4.6 | 3.8 |
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 | 38.1 | 45 | 38.1 |
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 | 0 |
Significant other observable inputs (Level II) | | | |
Asset of BSIF and consolidated Funds | | | |
Total fair value assets | 0 | 0 | 0 |
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 | 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 | 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 | 0 |
Significant unobservable inputs (Level III) | | | |
Asset of BSIF and consolidated Funds | | | |
Total fair value assets | 0 | 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 | 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 | 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 | $ 0 |