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Significant Transactions - NSM (Details) £ in Millions |  |  |  |  | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 07, 2020 USD ($) | Apr. 07, 2020 GBP (£) | Mar. 31, 2019 USD ($) | Dec. 03, 2018 USD ($) | May 18, 2018 USD ($) earnout_period | Mar. 31, 2021 USD ($) | Mar. 31, 2020 USD ($) | Sep. 30, 2019 USD ($) | Dec. 31, 2020 USD ($) | Apr. 07, 2020 GBP (£)
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
(Loss) gain on sale |  |  |  |  |  | $ 28,700,000 |  |  |  |
Goodwill |  |  |  |  |  | 613,400,000 |  |  | $ 525,500,000 |
Change in fair value of contingent consideration earnout liabilities |  |  |  |  |  | 0 | $ (600,000) |  |  |
Change in Fair Value of Contingent Earnout Liability, Expense (Revenue) Recognized |  |  |  |  |  | 0 | (600,000) |  |  |
Payment for Contingent Consideration Liability, Financing Activities |  |  |  |  |  | 6,700,000 | 6,400,000 |  |  |
NSM Insurance HoldCo, LLC |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Cash consideration to acquire businesses and interest in affiliates |  |  |  | $ 29,000,000.0 |  |  |  |  |  |
Fresh Insurance Services Group Limited |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest (as a percent) |  |  |  |  | 100.00% |  |  |  |  |
Equity method investment, aggregate cost |  |  |  |  | $ 49,600,000 |  |  |  |  |
Borrowings |  |  |  |  | $ 51,000,000.0 |  |  |  |  |
Purchase price adjustment |  |  |  |  |  |  |  | $ 700,000 |  |
Number of earnout periods | earnout_period |  |  |  |  | 2 |  |  |  |  |
KBK Insurance Group, Inc. & KBK Premium Services, Inc. |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Cash consideration to acquire businesses and interest in affiliates |  |  |  | 60,000,000.0 |  |  |  |  |  |
Borrowings |  |  |  | $ 30,100,000 |  |  |  |  |  |
Goodwill |  |  | $ 32,600,000 |  |  |  |  |  |  |
Intangible assets acquired |  |  | 32,700,000 |  |  |  |  |  |  |
Specialty Insurance Distribution (NSM) |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Contingent consideration earnout liabilities |  |  |  |  |  | 7,900,000 |  |  | $ 14,600,000 |
Specialty Insurance Distribution (NSM) | Kingsbridge Group Limited |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Equity method investment, aggregate cost | $ 132,200,000 |  |  |  |  |  |  |  |  | £ 107.2
Borrowings | $ 52,400,000 | £ 42.5 |  |  |  |  |  |  |  |
Percentage of voting interests acquired | 100.00% |  |  |  |  |  |  |  |  | 100.00%
Stock issued during period, value, acquisitions | $ 80,300,000 |  |  |  |  |  |  |  |  |
Acquisitions of businesses | 111,500,000 |  |  |  |  |  |  |  |  |
Attribution of acquisition date fair value estimates between goodwill and other intangible assets | 20,200,000 |  |  |  |  |  |  |  |  |
Contingent consideration related to the Ark Transaction | 4,100,000 |  |  |  |  | 200,000 |  |  |  |
Pretax income | 4,100,000 |  |  |  |  |  |  |  |  |
Foreign currency translation gain | $ 300,000 |  |  |  |  |  |  |  |  |
NSM Bank Facility | Specialty Insurance Distribution (NSM) |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Amount borrowed |  |  |  |  |  | $ 277,300,000 |  |  |  |
NSM Insurance HoldCo, LLC |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Ownership interest (as a percent) |  |  |  |  |  | 96.60% |  |  |  |
Fully diluted ownership interest (as a percent) |  |  |  |  |  | 89.60% |  |  |  |
KBK Insurance Group, Inc. & KBK Premium Services, Inc. |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Change in fair value of contingent consideration earnout liabilities |  |  | $ 5,900,000 |  |  |  |  |  |  |
Payment for Contingent Consideration Liability, Financing Activities |  |  |  |  |  | $ 6,700,000 | $ 6,400,000 |  |  |
KBK Insurance Group, Inc. & KBK Premium Services, Inc. | Specialty Insurance Distribution (NSM) |  |  |  |  |  |  |  |  |  |
Other Significant Noncash Transactions [Line Items] |  |  |  |  |  |  |  |  |  |
Contingent consideration earnout liabilities |  |  |  |  |  | $ 6,400,000 |  |  |  |

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