v3.26.3
Stockholders' Equity - Narrative (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended 9 Months Ended
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2023
shares
Sep. 30, 2026
USD ($)
vote
$ / shares
shares
Sep. 30, 2025
USD ($)
shares
Sep. 30, 2026
USD ($)
vote
$ / shares
shares
Sep. 30, 2025
USD ($)
shares
Dec. 31, 2025
$ / shares
shares
Class of Stock [Line Items]                
Units owned (in shares)       347,066,915 346,042,267 347,066,915 346,042,267  
Common stock, shares, issued (in shares)       347,066,915 346,042,267 347,066,915 346,042,267  
Preferred stock, shares authorized (in shares)       20,000,000   20,000,000    
Non-controlling interest | $       $ 35,300 $ 16,600 $ 35,300 $ 16,600  
Non-controlling interest unit holders | $       $ 10,295 $ 167 11,132 30,547  
HHC And Markel                
Class of Stock [Line Items]                
Total THG units exchanged (in shares)       18,473,911 9,481,750      
THG LLC                
Class of Stock [Line Items]                
Dividends, preferred stock, cash | $ $ 5,600 $ 5,600            
Non-controlling interest unit holders | $           11,100 30,500  
THG LLC | Hagerty, Inc.                
Class of Stock [Line Items]                
Non-controlling interest unit holders | $           5,100 11,900  
THG Unit Exchange                
Class of Stock [Line Items]                
General and administrative expenses | $           $ 800 $ 1,200  
Class A Common Stock                
Class of Stock [Line Items]                
Common stock, shares authorized (in shares)       500,000,000   500,000,000   500,000,000
Common stock, par value (in dollars per share) | $ / shares       $ 0.0001   $ 0.0001   $ 0.0001
Common stock, votes per share | vote       1   1    
Units owned (in shares)       120,569,434   120,569,434   100,706,893
Common stock, shares, issued (in shares)       120,569,434   120,569,434   100,706,893
Stock issued during period, shares, new issues (in shares)           30,526 33,550  
Total THG units exchanged (in shares)       18,498,911 9,484,250 18,923,313 9,562,552  
Class A Common Stock | HHC                
Class of Stock [Line Items]                
Total THG units exchanged (in shares)       10,637,500 9,481,750 10,637,500 9,481,750  
Number of shares issued in transaction (in shares)       10,637,500 9,481,750      
Class A Common Stock | 2021 Stock Incentive Plan                
Class of Stock [Line Items]                
Stock issued during period, shares, new issues (in shares)           908,702 797,980  
Class V Common Stock                
Class of Stock [Line Items]                
Common stock, shares authorized (in shares)       300,000,000   300,000,000   300,000,000
Common stock, par value (in dollars per share) | $ / shares       $ 0.0001   $ 0.0001   $ 0.0001
Common stock, votes per share | vote       10   10    
Units owned (in shares)       223,078,245   223,078,245   241,552,156
Common stock, shares, issued (in shares)       223,078,245   223,078,245   241,552,156
Common stock, conversion ratio           1    
Convertible Preferred Stock                
Class of Stock [Line Items]                
Preferred stock, par value (in dollars per share) | $ / shares       $ 0.0001   $ 0.0001    
Series A Convertible Preferred Stock                
Class of Stock [Line Items]                
Preferred stock, shares issued (in shares)       8,483,561   8,483,561   8,483,561
Preferred stock, shares outstanding (in shares)       8,483,561   8,483,561   8,483,561
Number of shares issued in transaction (in shares)     8,483,561          
Dividends, preferred stock, cash | $ $ 5,600 $ 5,600