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Derivatives - NSM Interest Rate Swap and Cap (Details) |  | 3 Months Ended | 6 Months Ended |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Aug. 18, 2020 | Jun. 30, 2021 USD ($) | Jun. 30, 2020 USD ($) | Jun. 30, 2021 USD ($) | Jun. 30, 2020 USD ($) | Mar. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Jun. 04, 2020 USD ($) | Jun. 04, 2020 GBP (£) | Apr. 07, 2020 USD ($) | Apr. 06, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Jun. 15, 2018 USD ($)
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt |  | $ 428,800,000 |  | $ 428,800,000 |  |  | $ 376,400,000 |  |  |  |  |  |  |
NSM Bank Facility | Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt |  | 269,400,000 |  | 269,400,000 |  |  | 271,300,000 |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt |  | $ 270,700,000 |  | $ 270,700,000 |  |  | 272,600,000 |  |  |  |  |  |  |
Weighted Average Interest rate |  | 8.50% | 7.30% | 8.50% | 7.30% |  |  |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) | Term loan - hedged |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted Average Interest rate |  | 9.20% | 8.60% | 9.20% | 8.60% |  |  |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) | Interest Rate Swap |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, fixed interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.97%
Derivative, variable interest rate |  | 1.00% |  | 1.00% |  |  |  |  |  |  |  |  |  |
Interest expense, net |  | $ 600,000 | $ 700,000 | $ 1,300,000 | $ 1,200,000 |  |  |  |  |  |  |  |  |
Derivative, fair value, net |  | 6,600,000 |  | 6,600,000 |  |  | 8,200,000 |  |  |  |  |  |  |
Change in fair value of derivative instruments |  | 600,000 | 400,000 | 1,600,000 | (2,800,000) |  |  |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) | Interest Rate Cap |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, fair value, net |  | $ 100,000 |  | 100,000 |  |  | 100,000 |  |  |  |  |  |  |
Premiums paid |  |  |  | $ 100,000 |  |  |  |  |  |  |  |  |  |
GBP-LIBOR rate |  | 0.08% |  | 0.08% |  |  |  |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) | Interest Rate Cap | GBP-LIBOR |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, cap interest rate |  | 1.25% |  | 1.25% |  |  |  |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) | NSM Bank Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total commitment under revolving credit facility |  |  |  |  |  |  |  |  |  | $ 291,400,000 | $ 234,000,000.0 |  |  |
Debt |  | $ 276,600,000 | $ 273,400,000 | $ 276,600,000 | $ 273,400,000 | $ 277,300,000 | $ 277,400,000 |  |  |  |  | $ 220,700,000 | $ 221,300,000 |
Specialty Insurance Distribution (NSM) | NSM Bank Facility | Interest Rate Swap | Term Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total commitment under revolving credit facility |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 151,000,000.0
Specialty Insurance Distribution (NSM) | NSM Bank Facility | Interest Rate Swap | Term Loan | Term loan - hedged |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt |  | $ 146,800,000 |  | $ 146,800,000 |  |  |  |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) | NSM Bank Facility | Interest Rate Cap |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, term extension | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) | NSM Bank Facility | Interest Rate Cap | United Kingdom, Pounds |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount | £ |  |  |  |  |  |  |  |  | £ 42,500,000 |  |  |  |  |
Specialty Insurance Distribution (NSM) | NSM Bank Facility | Interest Rate Cap | United States of America, Dollars |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  |  |  |  |  | $ 52,400,000 |  |  |  |  |  |

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