Contracts with Customers - Summary of Expected Revenue Related to Performance Obligations 1 (Detail) $ in Millions	Jun. 30, 2022 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 622.2
Brokerage [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	445.3
Risk Management [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 176.9