XML 62 R49.htm IDEA: XBRL DOCUMENT
v3.20.2

Loans and Allowance for Credit Losses on Loans - Credit Quality (Details) - USD ($) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2020 | Dec. 31, 2019
Loans by risk rating |  |
2020 | $ 469,211,000 |
2019 | 454,716,000 |
2018 | 297,078,000 |
2017 | 213,274,000 |
2016 | 153,838,000 |
Prior | 150,243,000 |
Revolving Loans | 291,967,000 |
Total loans, excluding PCI loans | 2,030,327,000 | $ 1,922,211,000
Total Loans | 2,030,327,000 | 1,930,812,000
Net loans | 1,997,409,000 | 1,911,023,000
Total Loans | 2,030,327,000 | 1,930,812,000
Minimum [Member] |  |
Loans by risk rating |  |
Loan commitment for inclusion in credit quality analysis | 50,000 |
Pass [Member] |  |
Loans by risk rating |  |
2020 | 462,620,000 |
2019 | 441,751,000 |
2018 | 284,526,000 |
2017 | 207,644,000 |
2016 | 145,944,000 |
Prior | 139,969,000 |
Revolving Loans | 283,056,000 |
Total Loans |  | 1,863,146,000
Net loans | 1,965,510,000 |
Special Mention [Member] |  |
Loans by risk rating |  |
2020 | 3,223,000 |
2019 | 2,363,000 |
2018 | 2,307,000 |
2017 | 2,706,000 |
2016 | 5,356,000 |
Prior | 16,000 |
Revolving Loans | 6,189,000 |
Total Loans |  | 26,886,000
Net loans | 22,160,000 |
Substandard [Member] |  |
Loans by risk rating |  |
2020 | 3,368,000 |
2019 | 10,602,000 |
2018 | 10,245,000 |
2017 | 2,924,000 |
2016 | 2,538,000 |
Prior | 10,258,000 |
Revolving Loans | 2,722,000 |
Total Loans |  | 40,780,000
Net loans | 42,657,000 |
PCI |  |
Loans by risk rating |  |
Total Loans |  | 8,601,000
PCI | Pass [Member] |  |
Loans by risk rating |  |
Total Loans |  | 573,000
PCI | Special Mention [Member] |  |
Loans by risk rating |  |
Total Loans |  | 261,000
PCI | Substandard [Member] |  |
Loans by risk rating |  |
Total Loans |  | 7,767,000
Non-PCI |  |
Loans by risk rating |  |
Total loans, excluding PCI loans |  | 1,922,211,000
Non-PCI | Pass [Member] |  |
Loans by risk rating |  |
Total loans, excluding PCI loans |  | 1,862,573,000
Non-PCI | Special Mention [Member] |  |
Loans by risk rating |  |
Total loans, excluding PCI loans |  | 26,625,000
Non-PCI | Substandard [Member] |  |
Loans by risk rating |  |
Total loans, excluding PCI loans |  | 33,013,000
Commercial |  |
Loans by risk rating |  |
2020 | 164,290,000 |
2019 | 44,118,000 |
2018 | 18,672,000 |
2017 | 7,228,000 |
2016 | 3,100,000 |
Prior | 2,784,000 |
Revolving Loans | 196,085,000 |
Total loans, excluding PCI loans |  | 332,842,000
Net loans | 436,277,000 |
Total Loans | 436,277,000 |
Commercial | Pass [Member] |  |
Loans by risk rating |  |
2020 | 161,595,000 |
2019 | 42,502,000 |
2018 | 16,568,000 |
2017 | 7,215,000 |
2016 | 3,096,000 |
Prior | 2,755,000 |
Revolving Loans | 188,270,000 |
Total loans, excluding PCI loans |  | 307,948,000
Net loans | 422,001,000 |
Commercial | Special Mention [Member] |  |
Loans by risk rating |  |
2020 | 443,000 |
2019 | 1,564,000 |
2018 | 68,000 |
2017 | 13,000 |
2016 | 4,000 |
Prior | 16,000 |
Revolving Loans | 6,176,000 |
Total loans, excluding PCI loans |  | 13,206,000
Net loans | 8,284,000 |
Commercial | Substandard [Member] |  |
Loans by risk rating |  |
2020 | 2,252,000 |
2019 | 52,000 |
2018 | 2,036,000 |
Prior | 13,000 |
Revolving Loans | 1,639,000 |
Total loans, excluding PCI loans |  | 11,688,000
Net loans | 5,992,000 |
Real estate - commercial | Commercial Real Estate, Owner Occupied General Purpose Loan [Member] |  |
Loans by risk rating |  |
Total Loans | 335,978,000 |
Real estate - commercial | Real estate - construction | Construction Real Estate, Homebuilder Loan [Member] |  |
Loans by risk rating |  |
Total Loans | 10,772,000 |
Real estate - residential |  |
Loans by risk rating |  |
Mortgage loans in process of foreclosure | 541,000 | 831,000
Leases |  |
Loans by risk rating |  |
2020 | 39,333,000 |
2019 | 57,977,000 |
2018 | 19,941,000 |
2017 | 7,819,000 |
2016 | 6,930,000 |
Prior | 1,676,000 |
Total loans, excluding PCI loans |  | 119,751,000
Net loans | 133,676,000 |
Total Loans | 133,676,000 |
Leases | Pass [Member] |  |
Loans by risk rating |  |
2020 | 39,333,000 |
2019 | 55,923,000 |
2018 | 18,937,000 |
2017 | 7,755,000 |
2016 | 6,463,000 |
Prior | 1,196,000 |
Total loans, excluding PCI loans |  | 119,045,000
Net loans | 129,607,000 |
Leases | Special Mention [Member] |  |
Loans by risk rating |  |
2019 | 799,000 |
Total loans, excluding PCI loans |  | 377,000
Net loans | 799,000 |
Leases | Substandard [Member] |  |
Loans by risk rating |  |
2019 | 1,255,000 |
2018 | 1,004,000 |
2017 | 64,000 |
2016 | 467,000 |
Prior | 480,000 |
Total loans, excluding PCI loans |  | 329,000
Net loans | 3,270,000 |
Commercial real estate - Investor |  |
Loans by risk rating |  |
2020 | 130,413,000 |
2019 | 172,286,000 |
2018 | 92,371,000 |
2017 | 70,566,000 |
2016 | 57,110,000 |
Prior | 25,356,000 |
Revolving Loans | 868,000 |
Total loans, excluding PCI loans |  | 520,095,000
Net loans | 548,970,000 |
Total Loans | 548,970,000 |
Commercial real estate - Investor | Pass [Member] |  |
Loans by risk rating |  |
2020 | 128,123,000 |
2019 | 168,503,000 |
2018 | 92,140,000 |
2017 | 70,566,000 |
2016 | 56,666,000 |
Prior | 24,362,000 |
Revolving Loans | 868,000 |
Total loans, excluding PCI loans |  | 510,640,000
Net loans | 541,228,000 |
Commercial real estate - Investor | Special Mention [Member] |  |
Loans by risk rating |  |
2020 | 1,816,000 |
2018 | 231,000 |
2016 | 99,000 |
Total loans, excluding PCI loans |  | 4,529,000
Net loans | 2,146,000 |
Commercial real estate - Investor | Substandard [Member] |  |
Loans by risk rating |  |
2020 | 474,000 |
2019 | 3,783,000 |
2016 | 345,000 |
Prior | 994,000 |
Total loans, excluding PCI loans |  | 4,926,000
Net loans | 5,596,000 |
Commercial real estate - Owner occupied |  |
Loans by risk rating |  |
2020 | 56,217,000 |
2019 | 57,156,000 |
2018 | 80,207,000 |
2017 | 49,764,000 |
2016 | 57,849,000 |
Prior | 33,702,000 |
Revolving Loans | 1,083,000 |
Total loans, excluding PCI loans |  | 345,504,000
Net loans | 335,978,000 |
Commercial real estate - Owner occupied | Pass [Member] |  |
Loans by risk rating |  |
2020 | 55,107,000 |
2019 | 54,702,000 |
2018 | 78,655,000 |
2017 | 45,928,000 |
2016 | 51,895,000 |
Prior | 30,174,000 |
Revolving Loans | 1,083,000 |
Total loans, excluding PCI loans |  | 330,891,000
Net loans | 317,544,000 |
Commercial real estate - Owner occupied | Special Mention [Member] |  |
Loans by risk rating |  |
2020 | 925,000 |
2018 | 464,000 |
2017 | 2,141,000 |
2016 | 5,246,000 |
Total loans, excluding PCI loans |  | 6,657,000
Net loans | 8,776,000 |
Commercial real estate - Owner occupied | Substandard [Member] |  |
Loans by risk rating |  |
2020 | 185,000 |
2019 | 2,454,000 |
2018 | 1,088,000 |
2017 | 1,695,000 |
2016 | 708,000 |
Prior | 3,528,000 |
Total loans, excluding PCI loans |  | 7,956,000
Net loans | 9,658,000 |
Construction |  |
Loans by risk rating |  |
2020 | 28,221,000 |
2019 | 43,360,000 |
2018 | 9,022,000 |
2017 | 589,000 |
2016 | 245,000 |
Prior | 1,283,000 |
Revolving Loans | 9,136,000 |
Total loans, excluding PCI loans |  | 69,617,000
Net loans | 91,856,000 |
Construction | Pass [Member] |  |
Loans by risk rating |  |
2020 | 28,182,000 |
2019 | 40,302,000 |
2018 | 6,972,000 |
2017 | 589,000 |
2016 | 245,000 |
Prior | 1,283,000 |
Revolving Loans | 9,136,000 |
Total loans, excluding PCI loans |  | 69,355,000
Net loans | 86,709,000 |
Construction | Special Mention [Member] |  |
Loans by risk rating |  |
2020 | 39,000 |
Net loans | 39,000 |
Construction | Substandard [Member] |  |
Loans by risk rating |  |
2019 | 3,058,000 |
2018 | 2,050,000 |
Total loans, excluding PCI loans |  | 262,000
Net loans | 5,108,000 |
Real estate - Investor |  |
Loans by risk rating |  |
2020 | 10,837,000 |
2019 | 14,632,000 |
2018 | 12,335,000 |
2017 | 8,488,000 |
2016 | 2,657,000 |
Prior | 12,458,000 |
Revolving Loans | 516,000 |
Total loans, excluding PCI loans |  | 71,105,000
Net loans | 61,923,000 |
Real estate - Investor | Commercial Real Estate, Non Owner Occupied General Purpose Loan [Member] |  |
Loans by risk rating |  |
Total Loans | 61,923,000 |
Real estate - Investor | Pass [Member] |  |
Loans by risk rating |  |
2020 | 10,497,000 |
2019 | 14,632,000 |
2018 | 11,721,000 |
2017 | 8,488,000 |
2016 | 2,558,000 |
Prior | 11,985,000 |
Revolving Loans | 516,000 |
Total loans, excluding PCI loans |  | 69,715,000
Net loans | 60,397,000 |
Real estate - Investor | Substandard [Member] |  |
Loans by risk rating |  |
2020 | 340,000 |
2018 | 614,000 |
2016 | 99,000 |
Prior | 473,000 |
Total loans, excluding PCI loans |  | 1,390,000
Net loans | 1,526,000 |
Real estate - Owner occupied |  |
Loans by risk rating |  |
2020 | 8,795,000 |
2019 | 23,545,000 |
2018 | 12,506,000 |
2017 | 19,017,000 |
2016 | 11,251,000 |
Prior | 36,487,000 |
Revolving Loans | 2,682,000 |
Total loans, excluding PCI loans |  | 136,023,000
Net loans | 114,283,000 |
Real estate - Owner occupied | Commercial Real Estate, Non Owner Occupied Special Purpose Loan [Member] |  |
Loans by risk rating |  |
Total Loans | 114,283,000 |
Real estate - Owner occupied | Pass [Member] |  |
Loans by risk rating |  |
2020 | 8,747,000 |
2019 | 23,545,000 |
2018 | 12,094,000 |
2017 | 18,796,000 |
2016 | 10,716,000 |
Prior | 33,867,000 |
Revolving Loans | 2,682,000 |
Total loans, excluding PCI loans |  | 132,258,000
Net loans | 110,447,000 |
Real estate - Owner occupied | Special Mention [Member] |  |
Loans by risk rating |  |
Total loans, excluding PCI loans |  | 134,000
Real estate - Owner occupied | Substandard [Member] |  |
Loans by risk rating |  |
2020 | 48,000 |
2018 | 412,000 |
2017 | 221,000 |
2016 | 535,000 |
Prior | 2,620,000 |
Total loans, excluding PCI loans |  | 3,631,000
Net loans | 3,836,000 |
Multifamily |  |
Loans by risk rating |  |
2020 | 27,925,000 |
2019 | 37,940,000 |
2018 | 49,522,000 |
2017 | 46,969,000 |
2016 | 13,269,000 |
Prior | 12,571,000 |
Revolving Loans | 202,000 |
Total loans, excluding PCI loans |  | 189,773,000
Net loans | 188,398,000 |
Multifamily | Commercial Real Estate, Retail Properties Loan [Member] |  |
Loans by risk rating |  |
Total Loans | 188,398,000 |
Multifamily | Pass [Member] |  |
Loans by risk rating |  |
2020 | 27,856,000 |
2019 | 37,940,000 |
2018 | 45,291,000 |
2017 | 45,516,000 |
2016 | 13,143,000 |
Prior | 10,514,000 |
Revolving Loans | 202,000 |
Total loans, excluding PCI loans |  | 187,560,000
Net loans | 180,462,000 |
Multifamily | Special Mention [Member] |  |
Loans by risk rating |  |
Total loans, excluding PCI loans |  | 1,710,000
Multifamily | Substandard [Member] |  |
Loans by risk rating |  |
2020 | 69,000 |
2018 | 2,687,000 |
2017 | 901,000 |
2016 | 119,000 |
Prior | 2,057,000 |
Total loans, excluding PCI loans |  | 503,000
Net loans | 5,833,000 |
Multifamily | Real estate - construction | Special Mention [Member] |  |
Loans by risk rating |  |
2018 | 1,544,000 |
2017 | 552,000 |
2016 | 7,000 |
Net loans | 2,103,000 |
HELOC |  |
Loans by risk rating |  |
2020 | 2,185,000 |
2019 | 2,287,000 |
2018 | 1,785,000 |
2017 | 2,508,000 |
2016 | 959,000 |
Prior | 1,290,000 |
Revolving Loans | 74,868,000 |
Total loans, excluding PCI loans |  | 91,605,000
Net loans | 85,882,000 |
Total Loans | 85,882,000 |
HELOC | Pass [Member] |  |
Loans by risk rating |  |
2020 | 2,185,000 |
2019 | 2,287,000 |
2018 | 1,697,000 |
2017 | 2,471,000 |
2016 | 694,000 |
Prior | 1,197,000 |
Revolving Loans | 73,772,000 |
Total loans, excluding PCI loans |  | 89,804,000
Net loans | 84,303,000 |
HELOC | Special Mention [Member] |  |
Loans by risk rating |  |
Revolving Loans | 13,000 |
Total loans, excluding PCI loans |  | 12,000
Net loans | 13,000 |
HELOC | Substandard [Member] |  |
Loans by risk rating |  |
2018 | 88,000 |
2017 | 37,000 |
2016 | 265,000 |
Prior | 93,000 |
Revolving Loans | 1,083,000 |
Total loans, excluding PCI loans |  | 1,789,000
Net loans | 1,566,000 |
HELOC - Purchased |  |
Loans by risk rating |  |
Prior | 22,312,000 |
Total loans, excluding PCI loans |  | 31,852,000
Net loans | 22,312,000 |
Total Loans | 22,312,000 |
HELOC - Purchased | Pass [Member] |  |
Loans by risk rating |  |
Prior | 22,312,000 |
Total loans, excluding PCI loans |  | 31,672,000
Net loans | 22,312,000 |
HELOC - Purchased | Substandard [Member] |  |
Loans by risk rating |  |
Total loans, excluding PCI loans |  | 180,000
Other 1 |  |
Loans by risk rating |  |
2020 | 995,000 |
2019 | 1,415,000 |
2018 | 717,000 |
2017 | 326,000 |
2016 | 468,000 |
Prior | 324,000 |
Revolving Loans | 6,527,000 |
Total loans, excluding PCI loans |  | 14,044,000
Net loans | 10,772,000 |
Other 1 | Pass [Member] |  |
Loans by risk rating |  |
2020 | 995,000 |
2019 | 1,415,000 |
2018 | 451,000 |
2017 | 320,000 |
2016 | 468,000 |
Prior | 324,000 |
Revolving Loans | 6,527,000 |
Total loans, excluding PCI loans |  | 13,685,000
Net loans | 10,500,000 |
Other 1 | Substandard [Member] |  |
Loans by risk rating |  |
2018 | 266,000 |
2017 | 6,000 |
Total loans, excluding PCI loans |  | $ 359,000
Net loans | $ 272,000 |

X
- Definition The amount of Financing Receivables that are prior loans. + References No definition available. + Details
Name: | osbc_FinancingReceivablePriorLoans
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, excluding PCI loans, before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References No definition available. + Details
Name: | osbc_LoansAndLeasesReceivableExcludingPCILoansNetOfDeferredIncome
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans and purchased credit impaired loans. Excludes loans and leases covered under loss sharing agreements. + References No definition available. + Details
Name: | osbc_LoansAndLeasesReceivableIncludingPurchasedCreditImpairedLoansNetOfDeferredIncome
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The outstanding loan commitment to be included in credit quality indicator analysis. + References No definition available. + Details
Name: | osbc_OutstandingLoanCommitmentsThresholdForCreditQualityCategorizing
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of financing receivable originated four years prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated in current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated in fiscal year prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 + Details
Name: | us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated three years prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated two years prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear
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_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of financing receivable that can be withdrawn, repaid and redrawn. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 + Details
Name: | us-gaap_FinancingReceivableRevolving
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5074-111524 + Details
Name: | us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 + Details
Name: | us-gaap_LoansAndLeasesReceivableNetReportedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 35 -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL49126937-111524 + Details
Name: | us-gaap_MortgageLoansInProcessOfForeclosureAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_PassMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditLossStatusAxis=us-gaap_FinancialAssetAcquiredWithCreditDeteriorationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditLossStatusAxis=us-gaap_FinancialAssetAcquiredAndNoCreditDeteriorationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=osbc_CommercialRealEstateOwnerOccupiedGeneralPurposeLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=osbc_ConstructionRealEstateHomebuilderLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_FinanceLeasesPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_CommercialRealEstateInvestorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_CommercialRealEstateOwnerOccupiedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConstructionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_RealEstateInvestorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=osbc_CommercialRealEstateNonOwnerOccupiedGeneralPurposeLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_RealEstateOwnerOccupiedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=osbc_CommercialRealEstateNonOwnerOccupiedSpecialPurposeLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_MultiFamilyLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=osbc_CommercialRealEstateRetailPropertiesLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_HomeEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_HelocPurchasedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=osbc_Other1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |