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v3.20.4

Employee Benefit Plans (Narrative) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 USD ($) $ / Family | Dec. 31, 2019 USD ($) | Jun. 30, 2019 USD ($) | Dec. 31, 2018 USD ($) | Jun. 30, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
401(k) deferred compensation and profit sharing plan, company contributions | $ 1,956 | $ 1,755 |  | $ 1,438 |
Annual losses per covered family | $ / Family | 175 |  |  |  |
Charges to earnings for self-insurance reserve | $ 5,234 | 5,495 |  | 3,724 |
Postretirement Medical and Life Benefit Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Estimated future employer contributions in 2021 | 96 |  |  |  |
Multi-Employer Pension Plan | Pentegra DB Plan |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Multiemployer plan, total contributions |  |  | $ 138,322 |  | $ 164,570
Multiemployer plan, maximum percentage of employer's contributions |  |  | 5.00% |  |
Multi-Employer Pension Plan | River Valley |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Pension expense | 42 | 84 |  |  |
Certain directors and officers |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Accrued benefits payable | 2,089 | 2,043 |  |  |
Deferred compensation expense | $ 304 | $ 243 |  | $ 324 |

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