XML 65 R48.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Summary of Significant Accounting Policies - Securities, Receivables, and Servicing Assets (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014
90-Days or Greater Past Due Loans |  |
Period from due date after which accrual of interest income is discontinued | 90 days |
Allowance for Loan Losses |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method | $ 1.3 |
Transfers and Servicing of Financial Assets |  |
Mortgage loans serviced for others | $ 638.2 | $ 604.2

X
- Definition Fair value as of the balance sheet date of mortgage loans representing net future revenues from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements. + References No definition available. + Details
Name: | osbc_MortgageLoansServicingAssetAtFairValueAmount
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the period from due date after which accrual of interest income is discontinued when full loan repayment is in doubt or when a loan becomes contractually past due. + References No definition available. + Details
Name: | osbc_PeriodFromDueDateAfterWhichAccrualOfInterestIncomeIsDiscontinued
Namespace Prefix: | osbc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition The effect of a change in method or methods for calculating the allowance for credit losses on the current period provision. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesEffectOfChangeInMethod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

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