XML 56 R45.htm IDEA: XBRL DOCUMENT v3.20.2
Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2020
Jan. 01, 2020
Dec. 31, 2019
Summary Of Significant Accounting Policies [Line Items]      
Retained income $ 198,092   $ 183,365
Minimum ownership interest percentage for limited partnerships accounted investments for using equity method 5.00%    
Unpaid earned premium and credit loss $ 0    
Allowance for uncollectible premiums $ 2,369   $ 528
Maximum [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Ownership interest to estimate net asset value method 5.00%    
Allowance for Credit Losses [Member] | Reinsurance Recoverable [Member] | ASU 2016-13 [Member]      
Summary Of Significant Accounting Policies [Line Items]      
Retained income   $ (453)