Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v3.20.4
Summary of Significant Accounting Policies - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2020
USD ($)
Segment
Unit
Dec. 31, 2019
USD ($)
Unit
Dec. 31, 2018
USD ($)
Jan. 01, 2019
USD ($)
Jun. 26, 2013
Summary Of Significant Accounting Policies [Line Items]          
Number of operating segment | Segment 1        
Cash equivalents, maximum maturity period 90 days        
Equity method investments, unrealized intercompany profit (loss) not eliminated amount $ 0        
Number of reporting unit | Unit 1 1      
Impairment charges on goodwill $ 0 $ 0 $ 0    
Operating lease liabilities 36,127,000 39,848,000      
Operating lease, ROU assets $ 30,068,000 33,485,000      
Accounting Standards Update 2016-02          
Summary Of Significant Accounting Policies [Line Items]          
Operating lease liabilities       $ 44,000,000.0  
Operating lease, ROU assets       $ 44,000,000.0  
ASU 2016-13          
Summary Of Significant Accounting Policies [Line Items]          
Change in accounting principle, accounting standards update, adoption date Jan. 01, 2020        
Change in accounting principle, accounting standards update, Adopted true        
Change in accounting principle, accounting standards update, Immaterial Effect true        
ASU 2017-04          
Summary Of Significant Accounting Policies [Line Items]          
Change in accounting principle, accounting standards update, Adopted true        
Change in accounting principle, accounting standards update, Immaterial Effect true        
Change in accounting principle, accounting standards update, Early Adoption true        
ASU 2018-15          
Summary Of Significant Accounting Policies [Line Items]          
Change in accounting principle, accounting standards update, adoption date Jan. 01, 2020        
Change in accounting principle, accounting standards update, Adopted true        
Change in accounting principle, accounting standards update, Immaterial Effect true        
Equity or Balanced Portfolios          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of asset management fee on threshold limit 1.00%        
Asset under management, threshold limit $ 10,000,000        
Percentage of asset management fee on balance 0.60%        
Fixed Income Portfolios          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of asset management fee on threshold limit 0.40%        
Asset under management, threshold limit $ 10,000,000        
Percentage of asset management fee on balance 0.30%        
Cortina Equity Portfolios          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of asset management fee on balance 0.80%        
Percentage of asset management fee on first threshold limit 1.00%        
Asset under management, first threshold limit $ 25,000,000        
Percentage of asset management fee on second threshold limit 0.90%        
Asset under management, second threshold limit $ 25,000,000        
Municipal Value Strategy          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of income from asset management fee 0.65%        
Outsourced Chief Investment Officer Portfolios          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of asset management fee on balance 0.24%        
Percentage of asset management fee on first threshold limit 0.40%        
Asset under management, first threshold limit $ 50,000,000        
Percentage of asset management fee on second threshold limit 0.32%        
Asset under management, second threshold limit $ 50,000,000        
Minimum          
Summary Of Significant Accounting Policies [Line Items]          
Identifiable finite-lived intangible assets, useful life 3 years        
Minimum | Private Funds          
Summary Of Significant Accounting Policies [Line Items]          
Prior written notice period to terminate investment management agreements 30 days        
Prior written notice period after receiving the affirmative vote, to terminate investment management agreements 60 days        
Percentage of income from asset management fee 0.25%        
Minimum | Non-discretionary Assets          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of income from asset management fee 0.05%        
Maximum          
Summary Of Significant Accounting Policies [Line Items]          
Identifiable finite-lived intangible assets, useful life 20 years        
Maximum | Private Funds          
Summary Of Significant Accounting Policies [Line Items]          
Prior written notice period to terminate investment management agreements 90 days        
Prior written notice period after receiving the affirmative vote, to terminate investment management agreements 90 days        
Percentage of income from asset management fee 1.50%        
Maximum | Non-discretionary Assets          
Summary Of Significant Accounting Policies [Line Items]          
Percentage of income from asset management fee 0.01%        
Leasehold Improvements          
Summary Of Significant Accounting Policies [Line Items]          
Property, plant and equipment, useful life 10 years        
Other Fixed Assets | Minimum          
Summary Of Significant Accounting Policies [Line Items]          
Property, plant and equipment, useful life 3 years        
Other Fixed Assets | Maximum          
Summary Of Significant Accounting Policies [Line Items]          
Property, plant and equipment, useful life 7 years        
Equity Method Investments          
Summary Of Significant Accounting Policies [Line Items]          
Impairment charges related to equity method investments $ 0 $ 0 $ 0    
Class A Common Stock          
Summary Of Significant Accounting Policies [Line Items]          
Common stock, voting rights one vote for each share        
Class B Common Stock          
Summary Of Significant Accounting Policies [Line Items]          
Common stock, voting rights one vote for each share        
Class of share exchangeable to another class one-for-one basis        
Silvercrest L.P | Class A Common Stock          
Summary Of Significant Accounting Policies [Line Items]          
Ownership percentage in a subsidiary 66.80% 64.80%     66.60%
Common stock, voting rights one vote for each share