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Corporate Structure (Narrative) (Details)
$ / shares in Units, $ in Millions
 3 Months Ended 9 Months Ended
Oct. 16, 2019
USD ($)
$ / shares
shares
Sep. 30, 2020
item
shares
Sep. 30, 2019
Sep. 30, 2020
item
shares
Sep. 30, 2019
Dec. 31, 2019
shares
Oct. 15, 2019
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]              
Common Stock, Shares, Outstanding | shares   19,472,310   19,472,310   19,473,818  
Exchange ratio   2.0212 2.0212 2.0212 2.0212    
Proceeds used to fund ESOP | $ $ 8.2            
Purchase by ESOP (in shares) | shares 816,992            
Number of banking offices | item   7   7      
Number of loan production offices | item   2   2      
Second-Step Stock Offering [Member]              
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]              
Proceeds from sale of common stock, net | $ $ 102.1            
Common stock, shares sold (in shares) | shares 10,212,397            
Common stock, share issue price per share (in dollars per share) | $ / shares $ 10.00            
Proceeds used to fund ESOP | $ $ 8.2            
Purchase by ESOP (in shares) | shares 816,992            
Purchase by ESOP (in dollars per share) | $ / shares $ 10.00            
Share issue, related expenses | $ $ 2.4            
Net proceeds invested in Bank's operations | $ $ 45.8            
Mutual Holding Company MHC [Member]              
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]              
Percentage of ownership (as a percent)             52.00%
Common Stock, Shares, Outstanding | shares 19,484,343            
Exchange ratio 2.0212