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Fair Values of Financial Instruments (Details) (USD $) | 3 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2014 | Dec. 31, 2014 | Dec. 31, 2013
Fair Values of Financial Instruments |  |  |
FHLBC Redemptions | $ 1,200,000 us-gaap_ProceedsFromSaleOfFederalHomeLoanBankStock |  |
Financial assets: |  |  |
Cash and due from banks |  | 30,101,000 us-gaap_CashAndDueFromBanks | 33,210,000 us-gaap_CashAndDueFromBanks
Interest bearing deposits with financial institutions |  | 14,096,000 us-gaap_InterestBearingDepositsInBanks | 14,450,000 us-gaap_InterestBearingDepositsInBanks
Fair Value |  | 385,486,000 us-gaap_AvailableForSaleSecurities | 372,191,000 us-gaap_AvailableForSaleSecurities
Securities held-to-maturity |  | 259,670,000 us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment | 256,571,000 us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
FHLBC and Reserve Bank Stock |  | 9,058,000 us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock | 10,292,000 us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock
Bank-owned life insurance |  | 56,807,000 us-gaap_BankOwnedLifeInsurance | 55,410,000 us-gaap_BankOwnedLifeInsurance
Financial liabilities: |  |  |
Noninterest bearing deposits |  | 400,447,000 us-gaap_NoninterestBearingDepositLiabilities | 373,389,000 us-gaap_NoninterestBearingDepositLiabilities
Other short-term borrowings |  | 45,000,000 us-gaap_OtherShortTermBorrowings | 5,000,000 us-gaap_OtherShortTermBorrowings
Junior subordinated debentures |  | 58,378,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust | 58,378,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust
Level 1 |  |  |
Financial assets: |  |  |
Cash and due from banks |  | 30,101,000 us-gaap_CashAndDueFromBanks / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 33,210,000 us-gaap_CashAndDueFromBanks / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Interest bearing deposits with financial institutions |  | 14,096,000 us-gaap_InterestBearingDepositsInBanks / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 14,450,000 us-gaap_InterestBearingDepositsInBanks / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Fair Value |  | 1,527,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 1,544,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Financial liabilities: |  |  |
Noninterest bearing deposits |  | 400,447,000 us-gaap_NoninterestBearingDepositLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 373,389,000 us-gaap_NoninterestBearingDepositLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Junior subordinated debentures |  | 32,441,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member | 39,777,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Borrowing interest payable |  |  | 10,122,000 us-gaap_InterestPayableCurrentAndNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member
Level 2 |  |  |
Financial assets: |  |  |
Fair Value |  | 330,900,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 216,385,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Securities held-to-maturity |  | 263,266,000 us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 254,328,000 us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
FHLBC and Reserve Bank Stock |  | 9,058,000 us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 10,292,000 us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Bank-owned life insurance |  | 56,807,000 us-gaap_BankOwnedLifeInsurance / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 55,410,000 us-gaap_BankOwnedLifeInsurance / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Loans held for sale |  | 5,072,000 us-gaap_LoansHeldForSaleFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 3,822,000 us-gaap_LoansHeldForSaleFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Accrued interest receivable |  | 4,888,000 us-gaap_InterestReceivable / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 4,248,000 us-gaap_InterestReceivable / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Financial liabilities: |  |  |
Interest bearing deposits |  | 1,284,887,000 us-gaap_InterestBearingDepositLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 1,312,476,000 us-gaap_InterestBearingDepositLiabilities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Securities sold under repurchase agreements |  | 21,036,000 us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 22,560,000 us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Other short-term borrowings |  | 45,000,000 us-gaap_OtherShortTermBorrowings / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 5,000,000 us-gaap_OtherShortTermBorrowings / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Junior subordinated debentures |  | 22,245,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 27,276,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Subordinated debenture |  | 39,366,000 us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 39,896,000 us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Note payable and other borrowings |  | 422,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 423,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Borrowing interest payable |  | 75,000 us-gaap_InterestPayableCurrentAndNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 6,915,000 us-gaap_InterestPayableCurrentAndNoncurrent / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Deposit interest payable |  | 467,000 osbc_DepositInterestPayableFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member | 762,000 osbc_DepositInterestPayableFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member
Level 3 |  |  |
Financial assets: |  |  |
Fair Value |  | 53,059,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 154,262,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Loans, net |  | 1,151,223,000 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 1,072,837,000 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member
Carrying Amount |  |  |
Financial assets: |  |  |
Cash and due from banks |  | 30,101,000 us-gaap_CashAndDueFromBanks / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 33,210,000 us-gaap_CashAndDueFromBanks / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Interest bearing deposits with financial institutions |  | 14,096,000 us-gaap_InterestBearingDepositsInBanks / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 14,450,000 us-gaap_InterestBearingDepositsInBanks / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Fair Value |  | 385,486,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 372,191,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Securities held-to-maturity |  | 259,670,000 us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 256,571,000 us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
FHLBC and Reserve Bank Stock |  | 9,058,000 us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 10,292,000 us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Bank-owned life insurance |  | 56,807,000 us-gaap_BankOwnedLifeInsurance / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 55,410,000 us-gaap_BankOwnedLifeInsurance / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Loans held for sale |  | 5,072,000 us-gaap_LoansHeldForSaleFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 3,822,000 us-gaap_LoansHeldForSaleFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Loans, net |  | 1,137,695,000 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 1,073,975,000 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Accrued interest receivable |  | 4,888,000 us-gaap_InterestReceivable / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 4,248,000 us-gaap_InterestReceivable / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Financial liabilities: |  |  |
Noninterest bearing deposits |  | 400,447,000 us-gaap_NoninterestBearingDepositLiabilities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 373,389,000 us-gaap_NoninterestBearingDepositLiabilities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Interest bearing deposits |  | 1,284,608,000 us-gaap_InterestBearingDepositLiabilities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 1,308,739,000 us-gaap_InterestBearingDepositLiabilities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Securities sold under repurchase agreements |  | 21,036,000 us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 22,560,000 us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Other short-term borrowings |  | 45,000,000 us-gaap_OtherShortTermBorrowings / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 5,000,000 us-gaap_OtherShortTermBorrowings / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Junior subordinated debentures |  | 58,378,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 58,378,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Subordinated debenture |  | 45,000,000 us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 45,000,000 us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Note payable and other borrowings |  | 500,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 500,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Borrowing interest payable |  | 75,000 us-gaap_InterestPayableCurrentAndNoncurrent / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 17,037,000 us-gaap_InterestPayableCurrentAndNoncurrent / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Deposit interest payable |  | 467,000 osbc_DepositInterestPayableFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember | 762,000 osbc_DepositInterestPayableFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_CarryingReportedAmountFairValueDisclosureMember
Total |  |  |
Financial assets: |  |  |
Cash and due from banks |  | 30,101,000 us-gaap_CashAndDueFromBanks / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 33,210,000 us-gaap_CashAndDueFromBanks / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Interest bearing deposits with financial institutions |  | 14,096,000 us-gaap_InterestBearingDepositsInBanks / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 14,450,000 us-gaap_InterestBearingDepositsInBanks / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Fair Value |  | 385,486,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 372,191,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Securities held-to-maturity |  | 263,266,000 us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 254,328,000 us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
FHLBC and Reserve Bank Stock |  | 9,058,000 us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 10,292,000 us-gaap_FederalHomeLoanBankStockAndFederalReserveBankStock / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Bank-owned life insurance |  | 56,807,000 us-gaap_BankOwnedLifeInsurance / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 55,410,000 us-gaap_BankOwnedLifeInsurance / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Loans held for sale |  | 5,072,000 us-gaap_LoansHeldForSaleFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 3,822,000 us-gaap_LoansHeldForSaleFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Loans, net |  | 1,151,223,000 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 1,072,837,000 us-gaap_LoansReceivableFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Accrued interest receivable |  | 4,888,000 us-gaap_InterestReceivable / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 4,248,000 us-gaap_InterestReceivable / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Financial liabilities: |  |  |
Noninterest bearing deposits |  | 400,447,000 us-gaap_NoninterestBearingDepositLiabilities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 373,389,000 us-gaap_NoninterestBearingDepositLiabilities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Interest bearing deposits |  | 1,284,887,000 us-gaap_InterestBearingDepositLiabilities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 1,312,476,000 us-gaap_InterestBearingDepositLiabilities / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Securities sold under repurchase agreements |  | 21,036,000 us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 22,560,000 us-gaap_SecuritiesLoanedOrSoldUnderAgreementsToRepurchaseFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Other short-term borrowings |  | 45,000,000 us-gaap_OtherShortTermBorrowings / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 5,000,000 us-gaap_OtherShortTermBorrowings / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Junior subordinated debentures |  | 54,686,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 67,053,000 us-gaap_JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Subordinated debenture |  | 39,366,000 us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 39,896,000 us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Note payable and other borrowings |  | 422,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 423,000 us-gaap_DebtInstrumentFairValue / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Borrowing interest payable |  | 75,000 us-gaap_InterestPayableCurrentAndNoncurrent / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | 17,037,000 us-gaap_InterestPayableCurrentAndNoncurrent / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember
Deposit interest payable |  | $ 467,000 osbc_DepositInterestPayableFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember | $ 762,000 osbc_DepositInterestPayableFairValueDisclosure / us-gaap_FairValueByMeasurementBasisAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember

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- Definition Represents the fair value of interest payable related to deposits at the balance sheet date. + References No definition available. + Details
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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
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- Definition The carrying amount of a life insurance policy on an officer, executive or employee for which the reporting entity (a bank) is entitled to proceeds from the policy upon death of the insured or surrender of the insurance policy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 10 -Article 9 + Details
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- Definition For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.1) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1, 2, 3 -Article 9 + Details
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- Definition Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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