XML 61 R49.htm IDEA: XBRL DOCUMENT v3.25.3

Loans and Allowance for Credit Losses on Loans - Major Classifications (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Loans
Total Loans	$ 5,265,014		$ 3,981,336
Allowance for credit losses	(75,037)	$ (42,990)	(43,619)	$ (44,422)	$ (42,269)	$ (44,264)
Net loans	5,189,977		3,937,717
Commercial
Loans
Total Loans	786,095		800,476
Allowance for credit losses	(10,342)	(7,185)	(7,813)	(9,685)	(6,728)	(3,998)
Leases
Loans
Total Loans	550,201		491,748
Allowance for credit losses	(2,403)	(2,280)	(2,136)	(1,975)	(1,978)	(2,952)
Commercial real estate - Investor
Loans
Total Loans	1,257,328		1,078,829
Allowance for credit losses	(20,977)	(16,922)	(14,528)	(16,837)	(17,842)	(17,105)
Commercial real estate - Owner occupied
Loans
Total Loans	680,412		683,283
Allowance for credit losses	(8,432)	(7,748)	(10,036)	(7,160)	(7,180)	(12,280)
Construction
Loans
Total Loans	176,387		201,716
Allowance for credit losses	(1,513)	(2,879)	(3,581)	(2,417)	(2,020)	(1,038)
Residential real estate - Investor
Loans
Total Loans	69,362		49,598
Allowance for credit losses	(767)	(565)	(553)	(564)	(609)	(669)
Residential real estate - Owner occupied
Loans
Total Loans	231,547		206,949
Allowance for credit losses	(1,905)	(1,926)	(1,509)	(1,740)	(1,618)	(1,821)
Multifamily
Loans
Total Loans	378,213		351,325
Allowance for credit losses	(1,730)	(1,707)	(1,876)	(2,463)	(2,804)	(2,728)
HELOC
Loans
Total Loans	234,885		103,388
Allowance for credit losses	(3,667)	$ (1,770)	(1,578)	$ (1,574)	$ (1,483)	$ (1,656)
Powersport
Loans
Total Loans	715,498
Allowance for credit losses	(17,006)
Other
Loans
Total Loans	$ 185,086		$ 14,024

X

- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable and net investment in lease.

+ References

No definition available.

+ Details

Name:	osbc_FinancingReceivableAndNetInvestmentInLeaseAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix:	osbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amortized cost excluding accrued interest, after allowance for credit loss, of financing receivable and net investment in lease.

+ References

No definition available.

+ Details

Name:	osbc_FinancingReceivableAndNetInvestmentInLeaseExcludingAccruedInterestAfterAllowanceForCreditLoss
Namespace Prefix:	osbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable and net investment in lease.

+ References

No definition available.

+ Details

Name:	osbc_FinancingReceivableAndNetInvestmentInLeaseExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	osbc_
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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 40
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481628/310-20-40-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

+ Details

Name:	us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_FinanceLeasesPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_CommercialRealEstateInvestorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_CommercialRealEstateOwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConstructionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_RealEstateInvestorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_RealEstateOwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_MultiFamilyLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_PowersportPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_Other2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: