XML 50 R38.htm IDEA: XBRL DOCUMENT
v3.24.2.u1

Securities - Contractual Maturities (Details) - USD ($) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 30, 2024 | Dec. 31, 2023
Securities Available-for-Sale, Amortized Cost |  |
Due in one year or less | $ 122,815 |
Due after one year through five years | 127,580 |
Due after five years through ten years | 58,374 |
Due after ten years | 156,872 |
Debt securities excluding securities not due at a single maturity date | 465,641 |
Total | $ 1,256,285 | $ 1,276,981
Securities Available-for-Sale, Weighted Average Yield |  |
Due in one year or less (as a percent) | 1.69% |
Due after one year through five years (as a percent) | 3.63% |
Due after five years through ten years (as a percent) | 2.77% |
Due after ten years (as a percent) | 3.11% |
Debt securities (as a percent) | 2.84% |
Total (as a percent) | 3.35% |
Securities Available-for-Sale, Fair Value |  |
Due in one year or less | $ 120,302 |
Due after one year through five years | 125,243 |
Due after five years through ten years | 53,383 |
Due after ten years | 149,909 |
Debt securities | 448,837 |
Debt Securities, Available-for-sale, Total | 1,173,661 | 1,192,829
Mortgage-backed and collateralized mortgage obligations |  |
Securities Available-for-Sale, Amortized Cost |  |
Securities not due at a single maturity date | $ 546,113 |
Securities Available-for-Sale, Weighted Average Yield |  |
Securities not due at a single maturity date, Weighted Average Yield (as a percent) | 2.52% |
Securities Available-for-Sale, Fair Value |  |
Securities not due at a single maturity date | $ 482,927 |
Asset-backed Securities |  |
Securities Available-for-Sale, Amortized Cost |  |
Securities not due at a single maturity date | 67,634 |
Total | $ 67,634 | 71,616
Securities Available-for-Sale, Weighted Average Yield |  |
Securities not due at a single maturity date, Weighted Average Yield (as a percent) | 4.08% |
Securities Available-for-Sale, Fair Value |  |
Securities not due at a single maturity date | $ 64,877 |
Debt Securities, Available-for-sale, Total | 64,877 | 68,436
Collateralized loan obligations. |  |
Securities Available-for-Sale, Amortized Cost |  |
Securities not due at a single maturity date | 176,897 |
Total | $ 176,897 | 173,201
Securities Available-for-Sale, Weighted Average Yield |  |
Securities not due at a single maturity date, Weighted Average Yield (as a percent) | 6.98% |
Securities Available-for-Sale, Fair Value |  |
Securities not due at a single maturity date | $ 177,020 |
Debt Securities, Available-for-sale, Total | $ 177,020 | $ 171,881

X
- Definition Amortized cost of debt securities categorized neither as held-to-maturity nor trading. This item represents the total amortized cost of all debt securities grouped by maturity dates, excluding the securities with no single maturity date. + References No definition available. + Details
Name: | osbc_AvailableForSaleDebtMaturitiesBeforeSecuritiesWithoutSingleMaturityDateAmortizedCostBasis
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of debt securities categorized neither as held-to-maturity nor trading. This item represents the total fair value of all debt securities grouped by maturity dates, excluding the securities with no single maturity date. + References No definition available. + Details
Name: | osbc_AvailableForSaleDebtMaturitiesBeforeSecuritiesWithoutSingleMaturityDateFairValue
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the weighted average yield of available-for-sale debt securities maturing after the tenth rolling twelve months following the latest balance sheet presented. This item represents the weighted average yield of all debt securities grouped by maturity dates, excluding the securities with no single maturity date. + References No definition available. + Details
Name: | osbc_AvailableForSaleDebtMaturitiesBeforeSecuritiesWithoutSingleMaturityDateWeightedAverageYield
Namespace Prefix: | osbc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the weighted average yield of available-for-sale debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. + References No definition available. + Details
Name: | osbc_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCostWeightedAverageYield
Namespace Prefix: | osbc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the weighted average yield of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. + References No definition available. + Details
Name: | osbc_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCostWeightedAverageYield
Namespace Prefix: | osbc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the weighted average yield of available-for-sale debt securities maturing after the tenth fiscal year following the latest fiscal year. + References No definition available. + Details
Name: | osbc_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCostWeightedAverageYield
Namespace Prefix: | osbc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | osbc_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostWeightedAverageYieldAbstract
Namespace Prefix: | osbc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the weighted average yield of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. + References No definition available. + Details
Name: | osbc_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCostWeightedAverageYield
Namespace Prefix: | osbc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the weighted average yield of available-for-sale debt securities that do not have a single maturity date and which the entity has decided to disclose separately rather than allocating the cost over several maturity groupings. + References No definition available. + Details
Name: | osbc_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateWeightedAverageYield
Namespace Prefix: | osbc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the weighted average yield of available-for-sale securities. + References No definition available. + Details
Name: | osbc_AvailableForSaleSecuritiesWeightedAverageYield
Namespace Prefix: | osbc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 320 -Name Accounting Standards Codification -Section 50 -Paragraph 3A -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480832/942-320-50-3A + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 320 -Name Accounting Standards Codification -Section 50 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480832/942-320-50-3A + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 320 -Name Accounting Standards Codification -Section 50 -Paragraph 3A -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480832/942-320-50-3A + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 320 -Name Accounting Standards Codification -Section 50 -Paragraph 3A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480832/942-320-50-3A + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), without single maturity date and not allocated over maturity grouping. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), without single maturity date and not allocated over maturity grouping. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 942 -SubTopic 320 -Name Accounting Standards Codification -Section 50 -Paragraph 3A -Publisher FASB -URI https://asc.fasb.org//1943274/2147480832/942-320-50-3A + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479130/326-30-45-1 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479130/326-30-45-1 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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