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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Mar. 31, 2020
Sep. 30, 2021
Sep. 30, 2020
Summary Of Significant Accounting Policy [Line Items]          
Tax benefit in other comprehensive income (loss) $ 37 $ 95   $ 85 $ 415
ASU 2016-13 [Member]          
Summary Of Significant Accounting Policy [Line Items]          
Change in Accounting Principle, Accounting Standards Update, Adopted [true false] true     true  
Change in Accounting Principle, Accounting Standards Update, Adoption Date Jan. 01, 2020     Jan. 01, 2020  
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false] true     true  
ASU 2019-12 [Member]          
Summary Of Significant Accounting Policy [Line Items]          
Change in Accounting Principle, Accounting Standards Update, Adopted [true false] true     true  
Change in Accounting Principle, Accounting Standards Update, Adoption Date Apr. 01, 2020     Apr. 01, 2020  
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false] true     true  
Adjustments for New Accounting Principle, Early Adoption [Member]          
Summary Of Significant Accounting Policy [Line Items]          
Tax benefit in other comprehensive income (loss)     $ (100)    
Overstatement Long-term Investment Balance at Remeasured Cost Basis [Member]          
Summary Of Significant Accounting Policy [Line Items]          
Amount of revision     2,800    
Errors in Net Investment Gain [Member]          
Summary Of Significant Accounting Policy [Line Items]          
Amount of revision     $ 1,500