XML 72 R56.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Cash and Due from Banks (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Other disclosures |  |
Balances | $ 10.8 | $ 11.0
Federal Reserve Bank average regulatory reserve |  |
Other disclosures |  |
Balances | $ 11.3 | $ 10.6

X
- Definition The amount of average compensating balance arrangement that is maintained with the Reserve Bank, under an agreement for a bank loan or future credit availability. + References No definition available. + Details
Name: | osbc_AverageReserveBalanceWithReserveBank
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of a specific compensating balance arrangement that is maintained under an agreement for a bank loan or future credit availability. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_CompensatingBalanceAmount
Namespace Prefix: | us-gaap_
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 No definition available. + Details
Name: | us-gaap_CompensatingBalancesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_CashAndCashEquivalentsAxis=osbc_FederalReserveBankRegulatoryReserveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |