Quarterly report pursuant to Section 13 or 15(d)

Marketable Securities - Summary of Company's Investment Securities (Detail)

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Marketable Securities - Summary of Company's Investment Securities (Detail) - USD ($)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Marketable Securities [Line Items]    
Cost $ 9,049 $ 5,014
Unrealized Gains 60 39
Unrealized Losses (1)
Fair Value 9,108 5,053
Exchange Traded Funds [Member]    
Marketable Securities [Line Items]    
Cost 1,306 713
Unrealized Gains 21 23
Unrealized Losses
Fair Value 1,327 736
Mutual Fund [Member]    
Marketable Securities [Line Items]    
Cost   4,301
Unrealized Gains   16
Unrealized Losses  
Fair Value   $ 4,317
Mutual Fund [Member] | BRIDGE INVESTMENT GROUP HOLDINGS LLC [Member]    
Marketable Securities [Line Items]    
Cost 7,743  
Unrealized Gains 39  
Unrealized Losses (1)  
Fair Value $ 7,781