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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

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