XML 79 R68.htm IDEA: XBRL DOCUMENT
v3.23.1

Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk - Commitments (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2023 | Dec. 31, 2022
Company's contractual commitments due to letters of credit |  |
Total letters of credit | $ 32,625,000 | $ 36,096,000
Allowance for credit loss on unfunded commitments | 3,200,000 |
Allowance for credit loss unfunded commitment, purchase accounting adjustment | 596,000 |
Decrease In allowance for credit loss on unfunded commitments | 1,400,000 |
Commercial unfunded commitments assumptions for decrease in the allowance for credit losses | 1,200,000 |
Accretion of interest income for decrease in the allowance for credit losses | 224,000 |
Fixed [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 5,369,000 | 6,675,000
Variable [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 27,256,000 | 29,421,000
Commitments to Extend Credit to Borrowers [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 32,558,000 | 36,029,000
Commitments to Extend Credit to Borrowers [Member] | Fixed [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 5,369,000 | 6,675,000
Commitments to Extend Credit to Borrowers [Member] | Variable [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 27,189,000 | 29,354,000
Commitments to Extend Credit to Borrowers [Member] | Financial Standby Letter of Credit [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 18,846,000 | 18,879,000
Commitments to Extend Credit to Borrowers [Member] | Financial Standby Letter of Credit [Member] | Fixed [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 3,456,000 | 3,514,000
Commitments to Extend Credit to Borrowers [Member] | Financial Standby Letter of Credit [Member] | Variable [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 15,390,000 | 15,365,000
Commitments to Extend Credit to Borrowers [Member] | Performance Guarantee [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 13,712,000 | 17,150,000
Commitments to Extend Credit to Borrowers [Member] | Performance Guarantee [Member] | Fixed [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 1,913,000 | 3,161,000
Commitments to Extend Credit to Borrowers [Member] | Performance Guarantee [Member] | Variable [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 11,799,000 | 13,989,000
Commitments to Extend Credit Nonborrowers [Member] | Performance Guarantee [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 67,000 | 67,000
Commitments to Extend Credit Nonborrowers [Member] | Performance Guarantee [Member] | Variable [Member] |  |
Company's contractual commitments due to letters of credit |  |
Total letters of credit | 67,000 | 67,000
Unused lines of Credit [Member] |  |
Company's contractual commitments due to letters of credit |  |
Loan commitments | 939,522,000 | 999,325,000
Unused lines of Credit [Member] | Fixed [Member] |  |
Company's contractual commitments due to letters of credit |  |
Loan commitments | 138,829,000 | 139,070,000
Unused lines of Credit [Member] | Variable [Member] |  |
Company's contractual commitments due to letters of credit |  |
Loan commitments | $ 800,693,000 | $ 860,255,000

X
- Definition Amount of accretion of interest income for decrease in the allowance for credit losses. + References No definition available. + Details
Name: | osbc_AccretionOfInterestIncomeForDecreaseInAllowanceForCreditLosses
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of allowance for credit loss on unfunded commitments. + References No definition available. + Details
Name: | osbc_AllowanceForCreditLossOnUnfundedCommitments
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of purchase accounting adjustment of allowance for credit loss unfunded commitment. + References No definition available. + Details
Name: | osbc_AllowanceForCreditLossUnfundedCommitmentPurchaseAccountingAdjustment
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of commercial unfunded commitments assumptions for increase (decrease) in the allowance for credit losses. + References No definition available. + Details
Name: | osbc_CommercialUnfundedCommitmentsAssumptionsForIncreaseDecreaseInAllowanceForCreditLosses
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of increase (decrease) in allowance for credit loss on unfunded commitments. + References No definition available. + Details
Name: | osbc_IncreaseDecreaseInAllowanceForCreditLossOnUnfundedCommitments
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Definition The face amount of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition. + References No definition available. + Details
Name: | us-gaap_FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
Name: | us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=osbc_FixedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=osbc_VariableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=osbc_CommitmentsToExtendCreditToBorrowersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_FinancialStandbyLetterOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_PerformanceGuaranteeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=osbc_CommitmentsToExtendCreditNonborrowersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_UnusedLinesOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |