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Retirement Benefits - Narrative (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]      
Requisite service period for employees to be eligible for 401(k) plan 3 months    
Percent of employer match on employee contributions 25.00%    
Percent of base compensation contributed by eligible employees 6.00%    
Contribution plan participation period (years) 3 years    
Contribution plan subsequent participation period (years) 3 years    
Requisite service period for members to become fully vested 5 years    
Company contribution amount $ 515 $ 508 $ 426
ESOP compensation expense 1,900 1,400 1,900
Estimated loss that will be amortized from accumulated other comprehensive income (loss) into net periodic cost 0    
Prior service cost (credit) that will be amortized from accumulated other comprehensive income (loss) into net periodic cost $ (19)    
Medical cost trend rate 8.75%    
Medical cost trend rate reduction percent per year 0.50%    
Medical cost trend rate ultimate rate 4.75%    
Benefits paid $ 99 97 103
Benefits expected to be paid under the postretirement health benefits plan in 2022 92    
Benefits expected to be paid under the postretirement health benefits plan in 2023 92    
Benefits expected to be paid under the postretirement health benefits plan in 2024 76    
Benefits expected to be paid under the postretirement health benefits plan in 2025 74    
Benefits expected to be paid under the postretirement health benefits plan in 2026 71    
Benefits expected to be paid under the postretirement health benefits plan in 2027 through 2031 306    
Supplemental Employee Retirement Plans, Defined Benefit      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation 16,500 15,500  
Net postretirement benefit cost included in compensation and employee benefits $ 1,700 1,600 2,000
Minimum      
Defined Benefit Plan Disclosure [Line Items]      
Percent of compensation employees can invest in 401(k) plan 2.00%    
Matching contribution percent 25.00%    
Maximum      
Defined Benefit Plan Disclosure [Line Items]      
Percent of compensation employees can invest in 401(k) plan 100.00%    
Matching contribution percent 50.00%    
First ESOP      
Defined Benefit Plan Disclosure [Line Items]      
Employee stock ownership plan, shares authorized and purchased (in shares) 2,463,884    
Initial public offering price (usd per share) $ 7.13    
Outstanding loan balance $ 8,500 $ 9,500  
Shares released and allocated to participants (in shares) 123,460 92,769  
Second ESOP      
Defined Benefit Plan Disclosure [Line Items]      
Employee stock ownership plan, shares authorized and purchased (in shares) 1,422,357    
Initial public offering price (usd per share) $ 10.00    
Outstanding loan balance $ 10,800 $ 11,300  
Shares released and allocated to participants (in shares) 59,064 54,986  
Supplemental ESOP      
Defined Benefit Plan Disclosure [Line Items]      
Company contribution to SESOP plan $ 41 $ 57 $ 41