General form of registration statement for all companies including face-amount certificate companies

Fair Value of Financial Instruments - Summary of Recurring basis (Detail)

v3.21.2
Fair Value of Financial Instruments - Summary of Recurring basis (Detail) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability $ 0    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   $ 0 $ 0
Financial liabilities 24,193 0  
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Public Placement Warrants [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability 24,193    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Private Warrants [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability 0    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Sponsor Shares [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability 0    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   0 0
Financial liabilities 0 0  
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Public Placement Warrants [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability 0    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Private Warrants [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability 0    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Sponsor Shares [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability 0    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   558 1
Financial liabilities 27,781 558  
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Public Placement Warrants [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability 0    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Private Warrants [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability 12,363    
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Sponsor Shares [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability $ 15,418    
Series B Preferred Stock Warrants [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   0 0
Series B Preferred Stock Warrants [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   0 0
Series B Preferred Stock Warrants [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   508 1
Series C Preferred Stock Warrants [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   0 0
Series C Preferred Stock Warrants [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   0 0
Series C Preferred Stock Warrants [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Derivative Liability   $ 50 $ 0