Employee Benefit Plans (Details) - USD ($) $ in Millions |
12 Months Ended | 24 Months Ended | |||
|---|---|---|---|---|---|
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2017 |
Dec. 31, 2019 |
|
| Employee Benefit Plans | |||||
| Expense relating to the 401(k) plan | $ 1.4 | $ 1.2 | $ 1.1 | ||
| Old Second Bancorp Inc Employees 401(k) Savings Plan and Trust | |||||
| Employee Benefit Plans | |||||
| Company's discretionary matching contributions to the Plan (as a percent) | 100.00% | ||||
| Company's discretionary matching contributions to the Plan (as a percent) | 50.00% | ||||
| Percentage of compensation contributed to the Plan matched by employer (as a percent) | 2.00% | ||||
| Percentage of compensation contributed to the Plan matched by employer | 3.00% | ||||
| Participants vesting as percentage of discretionary matching contributions | 100.00% | ||||