| Merger and Acquisitions - Additional Information (Detail) - USD ($) $ in Millions | 6 Months Ended | ||
|---|---|---|---|
| Dec. 01, 2021 | Jun. 30, 2022 | Dec. 31, 2021 | |
| Business Acquisition, Contingent Consideration [Line Items] | |||
| Maximum contingent consideration obligation | $ 72.5 | $ 129.2 | |
| Accounts Payable and Accrued Liabilities [Member] | |||
| Business Acquisition, Contingent Consideration [Line Items] | |||
| Business combination contingent consideration fair value current | 6.2 | 14.4 | |
| Other Non-Current Liabilities [Member] | |||
| Business Acquisition, Contingent Consideration [Line Items] | |||
| Business combination contingent consideration fair value non current | 20.2 | 27.6 | |
| Crouse And Associates Insurance Brokers Inc [Member] | |||
| Business Acquisition, Contingent Consideration [Line Items] | |||
| Total Consideration | $ 110.6 | ||
| Increase in assumed liability | 1.3 | ||
| Consideration transferred | 3.8 | ||
| Increase in goodwill | $ 5.1 | ||
| Keystone Risk Partners Llc [Member] | |||
| Business Acquisition, Contingent Consideration [Line Items] | |||
| Business combination assets acquired | $ 59.8 | 
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- Definition Business combination contingent consideration obligation related to acquisitions maximum. No definition available. 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled within one year or the normal operating cycle, if longer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled beyond one year or the normal operating cycle, if longer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of assets acquired at the acquisition date. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of liabilities due within one year or within the normal operating cycle, if longer, assumed at the acquisition date. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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