XML 27 R42.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans - Aging Analysis (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Aged analysis of past due loans      
30-59 Days Past Due $ 6,311us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue $ 1,978us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue  
60-89 Days Past Due 10us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue 987us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue  
Total Past Due 6,321us-gaap_FinancingReceivableRecordedInvestmentPastDue 2,965us-gaap_FinancingReceivableRecordedInvestmentPastDue  
Current 1,121,700us-gaap_FinancingReceivableRecordedInvestmentCurrent 1,129,441us-gaap_FinancingReceivableRecordedInvestmentCurrent  
Nonaccrual 23,048us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus 26,926us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus  
Total Loans 1,151,069us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome 1,159,332us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome 1,111,237us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Commercial      
Aged analysis of past due loans      
30-59 Days Past Due 684us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
38us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Total Past Due 684us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
38us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Current 120,311us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
125,658us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Nonaccrual 1,897us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
1,500us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Total Loans 122,892us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
127,196us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
107,548us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
Real estate - commercial      
Aged analysis of past due loans      
Total Loans 608,267us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
  579,297us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Real estate - commercial | Owner occupied general purpose      
Aged analysis of past due loans      
30-59 Days Past Due 2,921us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
699us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Total Past Due 2,921us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
699us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Current 127,156us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
126,029us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Nonaccrual 5,427us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
5,937us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Total Loans 135,504us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
132,665us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Real estate - commercial | Owner occupied special purpose      
Aged analysis of past due loans      
Current 170,733us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
167,874us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Nonaccrual 1,409us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,441us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Total Loans 172,142us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
169,315us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Real estate - commercial | Non-owner occupied general purpose      
Aged analysis of past due loans      
Current 151,033us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
153,328us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Nonaccrual 750us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
4,907us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Total Loans 151,783us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
158,235us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedGeneralPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Real estate - commercial | Non-owner occupied special purpose      
Aged analysis of past due loans      
Current 92,702us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
87,054us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Nonaccrual 1,198us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,423us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Total Loans 93,900us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
88,477us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateNonOwnerOccupiedSpecialPurposeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Real estate - commercial | Retail properties      
Aged analysis of past due loans      
Current 41,012us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateRetailPropertiesLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
37,780us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateRetailPropertiesLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Total Loans 41,012us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateRetailPropertiesLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
37,780us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateRetailPropertiesLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Real estate - commercial | Farm      
Aged analysis of past due loans      
Current 12,556us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateFarmLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
14,157us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateFarmLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Nonaccrual 1,370us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateFarmLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
   
Total Loans 13,926us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateFarmLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
14,157us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_CommercialRealEstateFarmLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
 
Real estate - construction      
Aged analysis of past due loans      
Total Loans 39,430us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
  32,016us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
Real estate - construction | Homebuilder      
Aged analysis of past due loans      
Current 2,660us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateHomebuilderLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
3,204us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateHomebuilderLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Total Loans 2,660us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateHomebuilderLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
3,204us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateHomebuilderLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Real estate - construction | Land      
Aged analysis of past due loans      
Current 2,463us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateLandLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
1,658us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateLandLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Total Loans 2,463us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateLandLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
1,658us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateLandLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Real estate - construction | Commercial speculative      
Aged analysis of past due loans      
Current 6,300us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateCommercialSpeculativeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
13,431us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateCommercialSpeculativeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Total Loans 6,300us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateCommercialSpeculativeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
13,431us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateCommercialSpeculativeLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Real estate - construction | All other      
Aged analysis of past due loans      
30-59 Days Past Due   71us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
60-89 Days Past Due   29us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Total Past Due   100us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Current 27,506us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
25,841us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Nonaccrual 501us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
561us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Total Loans 28,007us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
26,502us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ConstructionRealEstateOtherReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
 
Real estate - residential      
Aged analysis of past due loans      
Total Loans 363,967us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
  375,781us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Real estate - residential | Investor      
Aged analysis of past due loans      
30-59 Days Past Due 359us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialInvestorLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
   
Total Past Due 359us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialInvestorLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
   
Current 134,329us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialInvestorLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
135,273us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialInvestorLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Nonaccrual 1,160us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialInvestorLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
1,942us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialInvestorLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Total Loans 135,848us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialInvestorLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
137,215us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialInvestorLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Real estate - residential | Owner occupied      
Aged analysis of past due loans      
30-59 Days Past Due 2,092us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
1,076us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
60-89 Days Past Due   914us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Total Past Due 2,092us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
1,990us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Current 107,125us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
107,727us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Nonaccrual 6,745us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
6,711us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Total Loans 115,962us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
116,428us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialOwnerOccupiedLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Real estate - residential | Revolving and junior liens      
Aged analysis of past due loans      
30-59 Days Past Due 255us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
94us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
60-89 Days Past Due 10us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
44us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Total Past Due 265us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
138us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Current 109,301us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
113,906us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Nonaccrual 2,591us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
2,504us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Total Loans 112,157us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
116,548us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= osbc_ResidentialRevolvingAndJuniorLiensLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Consumer      
Aged analysis of past due loans      
Current 3,495us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
3,504us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Total Loans 3,495us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
3,504us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
2,837us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
All other      
Aged analysis of past due loans      
Current 13,018us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
13,017us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
 
Total Loans $ 13,018us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
$ 13,017us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
$ 13,758us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember