Related Party Transactions (Details) - 401(k) Savings Plan and Trust - USD ($) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Related Party Transactions | ||
| Current Value | $ 117,583,839 | $ 99,305,158 |
| Accounting and administrative services | $ 41,151 | |
| Company | Company stock | ||
| Related Party Transactions | ||
| Shares purchased | 47,506 | |
| Shares purchased at cost | $ 801,030 | |
| Shares sold | 85,616 | |
| Proceeds from shares sold | $ 1,557,378 | |
| Number of Units/Shares | 645,509 | 704,117 |
| Current Value | $ 12,587,426 | $ 12,519,200 |
| Dividends received | 172,432 | |
| Old Second National Bank | ||
| Related Party Transactions | ||
| Accounting and administrative services | 0 | |
| Accounting and administrative services paid by trustee | $ 107,155 |
| X | ||||||||||
- Definition Amount of administrative expenses incurred by trustee in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). No definition available.
|
| X | ||||||||||
- Definition Amount of decrease in net asset available for benefit from administrative expense incurred by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition Amount of increase in net asset available for benefit from dividend income on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition Cost of investment, excluding plan interest in master trust, acquired by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Fair value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract not meeting fully-benefit responsive investment criteria. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Number of shares or units of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Number of shares or units of investment purchased by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Number of shares or units of investment sold by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount of selling price for investment, excluding plan interest in master trust, sold by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|