XML 75 R60.htm IDEA: XBRL DOCUMENT v3.22.0.1

Loans and Allowance for Credit Losses on Loans - Major Classifications - Loan Concentrations (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Real estate | Loan receivables | Customer Concentration Risk
Loans
Loans receivable as a percentage of total portfolio	71.60%	72.50%

X

- Definition

Represents the percentage of total portfolio that is represented by a particular financial receivable category.

+ References

No definition available.

+ Details

Name:	osbc_LoansAndLeasesReceivableAsPercentageOfAggregatePortfolio
Namespace Prefix:	osbc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

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

X

- Details

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

X

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_AccountsReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: