XML 18 R65.htm IDEA: XBRL DOCUMENT
v3.20.1

Fair Value Measurements - Quantitative and Qualitative Information (Details) $ in Thousands | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Mar. 31, 2019 USD ($)
--- | --- | --- | ---
Quantitative information about Level 3 fair value measurements |  |  |
Mortgage servicing rights, fair value | $ 4,108 | $ 5,935 |
Securities available-for-sale, at fair value | 449,694 | 484,648 | $ 449,694
Level 3 |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Mortgage servicing rights, fair value | 4,108 | 5,935 |
Securities available-for-sale, at fair value | 11,157 | 5,419 |
US States and Political Subdivisions Debt Securities [Member] |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Securities available-for-sale, at fair value | 255,095 | 249,175 |
US States and Political Subdivisions Debt Securities [Member] | Level 3 |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Securities available-for-sale, at fair value | 11,200 | 19,600 |
Collateralized Mortgage Obligations [Member] |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Securities available-for-sale, at fair value | $ 53,403 | $ 57,984 |
Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Level 3 | Minimum [Member] |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Servicing Asset, Measurement Input | 10.0 | 10.0 |
Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Level 3 | Maximum [Member] |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Servicing Asset, Measurement Input | 17.0 | 58.8 |
Measurement Input, Discount Rate | Mortgage Servicing Rights [Member] | Level 3 | Weighted Average [Member] |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Servicing Asset, Measurement Input | 10.1 | 10.1 |
Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Level 3 | Minimum [Member] |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Servicing Asset, Measurement Input | 7.0 | 0.0 |
Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Level 3 | Maximum [Member] |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Servicing Asset, Measurement Input | 71.8 | 69.0 |
Measurement Input, Constant Prepayment Rate | Mortgage Servicing Rights [Member] | Level 3 | Weighted Average [Member] |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Servicing Asset, Measurement Input | 20.7 | 14.1 |
Recurring |  |  |
Quantitative information about Level 3 fair value measurements |  |  |
Securities available-for-sale, at fair value |  | $ 8,337 |

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122625-111746 + Details
Name: | us-gaap_ServicingAssetAtFairValueAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Value of input used to measure servicing asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
Name: | us-gaap_ServicingAssetMeasurementInput
Namespace Prefix: | us-gaap_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

X
- Details
Name: | us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputDiscountRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputConstantPrepaymentRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |