XML 51 R39.htm IDEA: XBRL DOCUMENT v3.25.2

Basis of Presentation and Changes in Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Millions				3 Months Ended		6 Months Ended
	Aug. 04, 2025	Jul. 15, 2025	Jul. 01, 2025	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Dividends declared per share				$ 0.06	$ 0.05	$ 0.12	$ 0.1
Subsequent Event | O 2025 Q3 Dividends
Dividends declared date		Jul. 15, 2025
Dividends declared per share		$ 0.06
Dividends payable date		Aug. 04, 2025
Dividends record date		Jul. 25, 2025
Dividends paid	$ 3.2
Subsequent Event | Bancorp Financial
Number of shares issued to each shareholder			2.5814
Amount of cash consideration transferred for each share			$ 15.93

X

- Definition

Number of shares issued to each shareholder in a business acquisition.

+ References

No definition available.

+ Details

Name:	osbc_BusinessAcquisitionNumberOfSharesIssuedToEachShareholder
Namespace Prefix:	osbc_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of cash consideration transferred for each share in a business combination.

+ References

No definition available.

+ Details

Name:	osbc_BusinessCombinationConsiderationTransferredPerShare
Namespace Prefix:	osbc_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

+ Details

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Date the declared dividend will be paid, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-3

+ Details

Name:	us-gaap_DividendPayableDateToBePaidDayMonthAndYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Date the dividend to be paid was declared, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-3

+ Details

Name:	us-gaap_DividendsPayableDateDeclaredDayMonthAndYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Date the holder must own the stock to be entitled to the dividend, in YYYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_DividendsPayableDateOfRecordDayMonthAndYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

+ Details

Name:	us-gaap_PaymentsOfDividends
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DividendsAxis=osbc_O2025Q3DividendsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_BusinessAcquisitionAxis=osbc_BancorpFinancialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: