Business Combinations - Acquisition Method for Recording Business Combinations (Detail)	3 Months Ended
	Mar. 31, 2022 USD ($)
Devitt Insurance Services Ltd [Member]
Business Acquisition [Line Items]
Cash Paid	$ 73,600,000
Accrued Liability	1,300,000
Escrow Deposited	3,400,000
Recorded Earnout Payable	12,500,000
Total Recorded Purchase Price	90,800,000
Maximum Potential Earnout Payable	12,500,000
Four Other Acquisitions [Member]
Business Acquisition [Line Items]
Cash Paid	16,300,000
Accrued Liability	2,400,000
Escrow Deposited	700,000
Recorded Earnout Payable	4,200,000
Total Recorded Purchase Price	23,600,000
Maximum Potential Earnout Payable	8,400,000
2022 Acquisitions [Member]
Business Acquisition [Line Items]
Cash Paid	89,900,000
Accrued Liability	3,700,000
Escrow Deposited	4,100,000
Recorded Earnout Payable	16,700,000
Total Recorded Purchase Price	114,400,000
Maximum Potential Earnout Payable	$ 20,900,000