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v3.25.1

Other Real Estate Owned (Tables) | 3 Months Ended
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Mar. 31, 2025
Other Real Estate Owned |
Schedule of activity in the other real estate owned (OREO) portfolio, net of valuation reserve | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended | ​
​ |  | March 31, |
Other real estate owned |  | 2025 |  | 2024 |
Balance at beginning of period | ​ | $ | 21,617 | ​ | $ | 5,123 | ​
Less: | ​ | ​ | ​ | ​ | ​ | ​ | ​
Carrying value of property disposals, net of participation sold | ​ | ​ | 18,285 | ​ | ​ | - | ​
Period valuation adjustments | ​ | ​ | 454 | ​ | ​ | - | ​
Balance at end of period | ​ | $ | 2,878 | ​ | $ | 5,123 | ​
Schedule of activity in valuation allowance | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Three Months Ended | ​
​ |  | March 31, |
​ |  | 2025 |  | 2024 |
Balance at beginning of period | ​ | $ | 1,862 | ​ | $ | 118 | ​
Provision for valuation reserves | ​ | ​ | 454 | ​ | ​ | - | ​
Reductions taken on sales | ​ | ​ | (1,463) | ​ | ​ | - | ​
Balance at end of period | ​ | $ | 853 | ​ | $ | 118 | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Schedule of expenses related to foreclosed assets, net of lease revenue | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended | ​
​ | ​ | March 31, |
​ |  | 2025 |  | 2024 |
Loss on sales, net | ​ | $ | 236 | ​ | $ | - | ​
Provision for valuation reserves | ​ | ​ | 454 | ​ | ​ | - | ​
Operating expenses | ​ | ​ | 1,913 | ​ | ​ | 113 | ​
Less: | ​ | ​ | ​ | ​ | ​ | ​ | ​
Lease revenue | ​ | ​ | 730 | ​ | ​ | 67 | ​
Net OREO expense | ​ | $ | 1,873 | ​ | $ | 46 | ​
​

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- Definition Tabular disclosure of expenses related to foreclosed assets, net of lease revenue. Foreclosed assets include all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings. + References No definition available. + Details
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Namespace Prefix: | osbc_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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- Definition Tabular disclosure of the change in valuation allowance of other real estate on properties acquired through foreclosure. + References No definition available. + Details
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Namespace Prefix: | osbc_
Data Type: | dtr-types:textBlockItemType
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- Definition Tabular disclosure of the change in other real estate on properties acquired through foreclosure. + References No definition available. + Details
Name: | osbc_RealEstateAcquiredThroughForeclosureRollForwardTableTextBlock
Namespace Prefix: | osbc_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_RealEstateAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration