Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023 USD ($) Country Segment Facility shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Significant Accounting Policies [Line Items]
Number of reportable segments | Segment	3
Number of commercial clean coal production facilities | Facility	35
Number of countries in which the company does business through a network of correspondent brokers and consultants | Country	130
Percentage of variable ownership interest	50.00%
Description of contracts renewal period	one year or less
Percentage of commission and fee revenues on the effective date	80.00%
Percentage of commission and fee revenues in the first three months	15.00%
Percentage of commission and fee revenues after the first three months	5.00%
Allowances for estimated policy cancellations	$ 9,900,000	$ 9,300,000
Allowance for doubtful accounts	$ 23,000,000	11,100,000
Premium financing contracts, terms	premium financing contracts are structured to minimize potential bad debt expense to us. Such receivables are generally considered delinquent after seven days of the payment due date. In normal course, insurance policies are canceled within one month of the contractual payment due date if the payment remains delinquent.
Outstanding loan receivable	$ 685,700,000	546,300,000
Write-off of amortizable intangible assets	$ 3,500,000	$ 2,000,000.0	$ 17,600,000
Impairment, Intangible Asset, Finite-Lived, Statement of Income or Comprehensive Income [Extensible Enumeration]	Depreciation, Amortization and Accretion, Net	Depreciation, Amortization and Accretion, Net	Depreciation, Amortization and Accretion, Net
Employee Stock Purchase Plan [Member]
Significant Accounting Policies [Line Items]
Shares authorized | shares	8,000,000.0
Percentage of employees contribution	15.00%
Purchase price of common stock, percentage	95.00%
Aggregate fair market value of shares purchased	$ 25,000
Maximum number of shares purchased by employees | shares	2,000
Shares available for grant | shares	5,000,000
Maximum [Member] | Partially Owned Entities [Member]
Significant Accounting Policies [Line Items]
Percentage of ownership interest	50.00%
Maximum [Member] | Expiration Lists [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of intangibles assets, years	15 years
Maximum [Member] | Non-Compete Agreements [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of intangibles assets, years	6 years
Maximum [Member] | Trade Names [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of intangibles assets, years	15 years
Minimum [Member] | Majority-owned Subsidiaries [Member]
Significant Accounting Policies [Line Items]
Percentage of ownership interest	50.00%
Minimum [Member] | Expiration Lists [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of intangibles assets, years	2 years
Minimum [Member] | Non-Compete Agreements [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of intangibles assets, years	2 years
Minimum [Member] | Trade Names [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives of intangibles assets, years	2 years