Annual report pursuant to Section 13 and 15(d)

Acquisitions - Additional Information (Detail)

v3.20.4
Acquisitions - Additional Information (Detail) - USD ($)
3 Months Ended 12 Months Ended
Jul. 01, 2019
Apr. 12, 2019
Dec. 13, 2018
Dec. 15, 2015
Mar. 30, 2015
Dec. 31, 2020
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Business Acquisition [Line Items]                                
Revenue           $ 28,415,000 $ 27,182,000 $ 24,021,000 $ 28,365,000 $ 27,838,000 $ 27,845,000 $ 23,897,000 $ 22,572,000 $ 107,983,000 $ 102,152,000 $ 98,673,000
Income before provision for income taxes                           22,872,000 20,590,000 22,826,000
Contingent purchase price payment                           741,000 425,000 447,000
Cortina Asset Management, LLC                                
Business Acquisition [Line Items]                                
Aggregate purchase amount                           57,824,000    
Equity consideration for SLP acquired           15,100,000       14,000,000       15,100,000 14,000,000  
Fair value adjustments to contingent purchase price consideration                           1,100,000 200,000  
Revenue                           11,642,000 6,241,000  
Income before provision for income taxes                           3,016,000 1,923,000  
Cash paid on date of acquisition                             35,169,000  
Cash paid on date of acquisition                           17,072,000    
Cortina Asset Management, LLC | General, Administrative and Other                                
Business Acquisition [Line Items]                                
Costs related to acquisition                           90,000 1,148,000  
Cortina Asset Management, LLC | Purchase Agreement                                
Business Acquisition [Line Items]                                
Aggregate purchase amount $ 33,577,000                              
Percentage to acquire business in cash   80.00%                            
Additional percentage to acquire business in cash 80.00% 80.00%                            
Business combination consideration partially offset by net closing credits $ 35,072,000                              
Equity consideration for SLP acquired 13,800,000                              
Business combination acquired revenue   $ 13,027,000                            
Cortina Asset Management, LLC | Purchase Agreement | Revenue Greater than or Equal to 95% for July 1, 2020 to June 30, 2021                                
Business Acquisition [Line Items]                                
Business combination contingent consideration first retention payment   3,370,000                            
Cortina Asset Management, LLC | Purchase Agreement | Revenue Equal to 75% or Less for July 1, 2020 to June 30, 2021                                
Business Acquisition [Line Items]                                
Business combination contingent consideration first retention payment   0                            
Cortina Asset Management, LLC | Purchase Agreement | Revenue Between 75% and 95% for July 1, 2020 to June 30, 2021                                
Business Acquisition [Line Items]                                
Business combination contingent consideration first retention payment, minimum   0                            
Business combination contingent consideration first retention payment, maximum   3,370,000                            
Cortina Asset Management, LLC | Purchase Agreement | Revenue Between 85% and 105% for July 1, 2021 to June 30, 2022                                
Business Acquisition [Line Items]                                
Business combination contingent consideration second retention payment, minimum   0                            
Business combination contingent consideration second retention payment, maximum   5,617,000                            
Cortina Asset Management, LLC | Purchase Agreement | Revenue Equal to 85% or Less for July 1, 2021 to June 30, 2022                                
Business Acquisition [Line Items]                                
Business combination contingent consideration second retention payment   0                            
Cortina Asset Management, LLC | Purchase Agreement | Revenue Between 95% and 140% for July 1, 2022 to June 30, 2023                                
Business Acquisition [Line Items]                                
Business combination contingent consideration growth payment, minimum   0                            
Business combination contingent consideration growth payment, maximum   17,222,000                            
Cortina Asset Management, LLC | Purchase Agreement | Revenue Equal to 95% or Less for July 1, 2022 to June 30, 2023                                
Business Acquisition [Line Items]                                
Business combination contingent consideration growth payment   0                            
Cortina Asset Management, LLC | Purchase Agreement | Maximum                                
Business Acquisition [Line Items]                                
Aggregate purchase amount   44,937,000                            
Additional aggregate purchase amount 26,209,000 26,209,000                            
Cortina Asset Management, LLC | Purchase Agreement | Maximum | Revenue Between 85% and 105% for July 1, 2021 to June 30, 2022                                
Business Acquisition [Line Items]                                
Business combination contingent consideration second retention payment   5,617,000                            
Cortina Asset Management, LLC | Purchase Agreement | Maximum | Revenue Between 95% and 140% for July 1, 2022 to June 30, 2023                                
Business Acquisition [Line Items]                                
Business combination contingent consideration growth payment   $ 17,222,000                            
Cortina Asset Management, LLC | Purchase Agreement | Silvercrest L.P                                
Business Acquisition [Line Items]                                
Percentage of business combination consideration issuance   20.00%                            
Additional aggregate purchase amount $ 8,952,000                              
Additional percentage of earn out payment paid in cash 20.00% 20.00%                            
Potential earn-out payments period 4 years 4 years                            
Issuance of Class B shares, Shares 662,713                              
Neosho                                
Business Acquisition [Line Items]                                
Equity consideration for SLP acquired     $ 20,000     1,028,000       1,403,000       1,028,000 1,403,000  
Fair value adjustments to contingent purchase price consideration                           (75,000) (283,000)  
Cash paid on date of acquisition     399,000                       399,000  
Contingent consideration     1,686,000                          
Expected payments on first anniversary of closing date     300,000                          
Earn out payments due in two years     100,000                          
Earn out payments due in three years     100,000                          
Earn out payments due in four years     100,000                          
Earn out payments due in five years     $ 100,000                          
Percentage of product to obtain earn out payment     50.00%                          
Percentage of earn out payment paid in cash     75.00%                          
Percentage of earn out payment paid in equity     25.00%                          
Contingent purchase price payment                           300,000    
Cappiccille                                
Business Acquisition [Line Items]                                
Equity consideration for SLP acquired           114,000       101,000       114,000 101,000  
Fair value adjustments to contingent purchase price consideration                           126,000 (25,000) 54,000
Contingent consideration       $ 354,000                        
Contingent purchase price payment                           113,000 105,000  
Cash paid on date of acquisition       $ 148,000                        
Earn out payments percentage on revenue remainder of fiscal year       19.00%                        
Earn out payments percentage on revenue due in two years       19.00%                        
Earn out payments percentage on revenue due in three years       19.00%                        
Earn out payments percentage on revenue due in four years       19.00%                        
Earn out payments percentage on revenue due thereafter       19.00%                        
Jamison                                
Business Acquisition [Line Items]                                
Equity consideration for SLP acquired         $ 3,562,000 $ 160,000       $ 418,000       160,000 418,000  
Fair value adjustments to contingent purchase price consideration                           70,000 214,000 $ 52,000
Contingent consideration         1,429,000                      
Contingent purchase price payment                           $ 328,000 $ 320,000  
Cash paid on date of acquisition         $ 3,550,000                      
Earn out payments percentage on EBITDA remainder of fiscal year         20.00%                      
Earn out payments percentage on EBITDA due in two years         20.00%                      
Earn out payments percentage on EBITDA due in three years         20.00%                      
Earn out payments percentage on EBITDA due in four years         20.00%                      
Earn out payments percentage on EBITDA due in five years         20.00%                      
Earn Out Payments Percentage On EBITDA Due thereafter         20.00%                      
Jamison | Seller Note                                
Business Acquisition [Line Items]                                
Promissory note issued         $ 394,000                      
Interest on principal amount         5.00%                      
Jamison | Principals Notes                                
Business Acquisition [Line Items]                                
Promissory note issued         $ 1,771,000                      
Interest on principal amount         5.00%