Quarterly report pursuant to Section 13 or 15(d)

Revenue - Summary of Disaggregation of Revenue, Transaction Fees (Detail)

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Revenue - Summary of Disaggregation of Revenue, Transaction Fees (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Disaggregation of Revenue [Line Items]        
Revenue $ 92,171 $ 51,352 $ 222,695 $ 160,203
Transaction Fees [Member]        
Disaggregation of Revenue [Line Items]        
Revenue 21,907 5,085 43,475 20,724
Transaction Fees [Member] | Acquisition Fees [Member]        
Disaggregation of Revenue [Line Items]        
Revenue 19,838 3,793 37,627 15,877
Transaction Fees [Member] | Brokerage Fees [Member]        
Disaggregation of Revenue [Line Items]        
Revenue $ 2,069 $ 1,292 $ 5,848 $ 4,847