XML 61 R50.htm IDEA: XBRL DOCUMENT
v3.22.2.2

Loans and Allowance for Credit Losses on Loans - Credit Quality (Details) - USD ($) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2022 | Dec. 31, 2021
Loans by risk rating |  |
2022 / 2021 | $ 974,030,000 |
2021 / 2020 | 909,798,000 | $ 1,117,231,000
2020 / 2019 | 506,839,000 | 617,495,000
2019 / 2018 | 291,281,000 | 438,126,000
2018 / 2017 | 194,274,000 | 273,820,000
2017 / 2016 |  | 183,708,000
Prior | 278,728,000 | 234,222,000
Revolving Loans | 713,756,000 | 556,172,000
Revolving Loans Converted To Term Loans | 628,000 | 30,000
Total Loans | 3,869,334,000 | 3,420,804,000
Minimum |  |
Loans by risk rating |  |
Loan commitment for inclusion in credit quality analysis | 50,000 |
Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 946,621,000 | 1,079,972,000
2021 / 2020 | 873,420,000 | 607,575,000
2020 / 2019 | 442,402,000 | 392,999,000
2019 / 2018 | 196,825,000 | 267,763,000
2018 / 2017 | 193,016,000 | 177,970,000
Prior | 264,572,000 | 224,824,000
Revolving Loans | 686,455,000 | 546,694,000
Revolving Loans Converted To Term Loans | 628,000 | 30,000
Total Loans | 3,603,939,000 | 3,297,827,000
Special Mention [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 16,812,000 | 16,169,000
2021 / 2020 | 13,796,000 | 2,222,000
2020 / 2019 | 59,754,000 | 26,029,000
2019 / 2018 | 38,693,000 |
2018 / 2017 | 244,000 |
Prior | 4,217,000 |
Revolving Loans | 18,149,000 | 3,816,000
Total Loans | 151,665,000 | 48,236,000
Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 10,597,000 | 21,090,000
2021 / 2020 | 22,582,000 | 7,698,000
2020 / 2019 | 4,683,000 | 19,098,000
2019 / 2018 | 55,763,000 | 6,057,000
2018 / 2017 | 1,014,000 | 5,738,000
Prior | 9,939,000 | 9,398,000
Revolving Loans | 9,152,000 | 5,662,000
Total Loans | 113,730,000 | 74,741,000
Commercial |  |
Loans by risk rating |  |
2022 / 2021 | 178,865,000 | 201,800,000
2021 / 2020 | 83,467,000 | 54,770,000
2020 / 2019 | 28,367,000 | 53,429,000
2019 / 2018 | 30,032,000 | 28,503,000
2018 / 2017 | 8,517,000 | 5,176,000
Prior | 5,313,000 | 11,020,000
Revolving Loans | 553,047,000 | 416,746,000
Revolving Loans Converted To Term Loans | 473,000 | 30,000
Total Loans | 888,081,000 | 771,474,000
Commercial | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 170,428,000 | 192,258,000
2021 / 2020 | 77,354,000 | 50,638,000
2020 / 2019 | 23,879,000 | 38,614,000
2019 / 2018 | 14,671,000 | 28,177,000
2018 / 2017 | 8,502,000 | 5,176,000
Prior | 5,253,000 | 10,945,000
Revolving Loans | 527,792,000 | 408,394,000
Revolving Loans Converted To Term Loans | 473,000 | 30,000
Total Loans | 828,352,000 | 734,232,000
Commercial | Special Mention [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 3,030,000 | 44,000
2021 / 2020 | 3,137,000 | 84,000
2020 / 2019 | 1,274,000 | 694,000
2019 / 2018 | 2,528,000 |
Revolving Loans | 18,038,000 | 3,708,000
Total Loans | 28,007,000 | 4,530,000
Commercial | Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 5,407,000 | 9,498,000
2021 / 2020 | 2,976,000 | 4,048,000
2020 / 2019 | 3,214,000 | 14,121,000
2019 / 2018 | 12,833,000 | 326,000
2018 / 2017 | 15,000 |
Prior | 60,000 | 75,000
Revolving Loans | 7,217,000 | 4,644,000
Total Loans | 31,722,000 | 32,712,000
Real estate - residential |  |
Loans by risk rating |  |
Mortgage loans in process of foreclosure | 659,000 | 488,000
Leases |  |
Loans by risk rating |  |
2022 / 2021 | 122,629,000 | 83,402,000
2021 / 2020 | 69,757,000 | 44,129,000
2020 / 2019 | 30,508,000 | 35,093,000
2019 / 2018 | 21,673,000 | 9,573,000
2018 / 2017 | 5,628,000 | 1,170,000
Prior | 1,408,000 | 2,664,000
Total Loans | 251,603,000 | 176,031,000
Leases | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 122,629,000 | 83,402,000
2021 / 2020 | 69,757,000 | 44,129,000
2020 / 2019 | 30,415,000 | 32,259,000
2019 / 2018 | 21,531,000 | 8,950,000
2018 / 2017 | 5,628,000 | 1,170,000
Prior | 1,408,000 | 2,367,000
Total Loans | 251,368,000 | 172,277,000
Leases | Substandard [Member] |  |
Loans by risk rating |  |
2020 / 2019 | 93,000 | 2,834,000
2019 / 2018 | 142,000 | 623,000
Prior |  | 297,000
Total Loans | 235,000 | 3,754,000
Commercial real estate - Investor |  |
Loans by risk rating |  |
2022 / 2021 | 340,673,000 | 263,050,000
2021 / 2020 | 240,919,000 | 177,596,000
2020 / 2019 | 148,301,000 | 129,698,000
2019 / 2018 | 88,953,000 | 85,230,000
2018 / 2017 | 49,805,000 | 68,422,000
Prior | 66,299,000 | 57,330,000
Revolving Loans | 6,960,000 | 18,602,000
Total Loans | 941,910,000 | 799,928,000
Commercial real estate - Investor | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 335,320,000 | 245,346,000
2021 / 2020 | 238,901,000 | 175,218,000
2020 / 2019 | 148,301,000 | 118,697,000
2019 / 2018 | 65,813,000 | 85,049,000
2018 / 2017 | 49,805,000 | 64,810,000
Prior | 60,056,000 | 55,523,000
Revolving Loans | 6,960,000 | 18,602,000
Total Loans | 905,156,000 | 763,245,000
Commercial real estate - Investor | Special Mention [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 5,353,000 | 15,466,000
2020 / 2019 |  | 10,550,000
Prior | 3,149,000 |
Total Loans | 8,502,000 | 26,016,000
Commercial real estate - Investor | Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 |  | 2,238,000
2021 / 2020 | 2,018,000 | 2,378,000
2020 / 2019 |  | 451,000
2019 / 2018 | 23,140,000 | 181,000
2018 / 2017 |  | 3,612,000
Prior | 3,094,000 | 1,807,000
Total Loans | 28,252,000 | 10,667,000
Commercial real estate - Owner occupied |  |
Loans by risk rating |  |
2022 / 2021 | 175,121,000 | 298,543,000
2021 / 2020 | 267,587,000 | 156,295,000
2020 / 2019 | 157,986,000 | 94,964,000
2019 / 2018 | 86,393,000 | 60,915,000
2018 / 2017 | 51,643,000 | 55,487,000
Prior | 104,468,000 | 63,119,000
Revolving Loans | 33,753,000 | 2,522,000
Total Loans | 876,951,000 | 731,845,000
Commercial real estate - Owner occupied | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 164,067,000 | 290,225,000
2021 / 2020 | 241,671,000 | 155,353,000
2020 / 2019 | 103,552,000 | 90,325,000
2019 / 2018 | 48,982,000 | 60,915,000
2018 / 2017 | 51,399,000 | 54,236,000
Prior | 100,087,000 | 59,887,000
Revolving Loans | 33,753,000 | 2,522,000
Total Loans | 743,511,000 | 713,463,000
Commercial real estate - Owner occupied | Special Mention [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 8,429,000 |
2021 / 2020 | 8,600,000 |
2020 / 2019 | 53,299,000 | 2,953,000
2019 / 2018 | 19,102,000 |
2018 / 2017 | 244,000 |
Prior | 1,068,000 |
Total Loans | 90,742,000 | 2,953,000
Commercial real estate - Owner occupied | Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 2,625,000 | 8,318,000
2021 / 2020 | 17,316,000 | 942,000
2020 / 2019 | 1,135,000 | 1,686,000
2019 / 2018 | 18,309,000 |
2018 / 2017 |  | 1,251,000
Prior | 3,313,000 | 3,232,000
Total Loans | 42,698,000 | 15,429,000
Construction |  |
Loans by risk rating |  |
2022 / 2021 | 28,609,000 | 88,780,000
2021 / 2020 | 79,090,000 | 67,767,000
2020 / 2019 | 49,319,000 | 42,101,000
2019 / 2018 | 12,801,000 | 4,671,000
2018 / 2017 | 2,886,000 | 477,000
Prior | 1,435,000 | 1,193,000
Revolving Loans | 2,560,000 | 1,143,000
Total Loans | 176,700,000 | 206,132,000
Construction | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 27,377,000 | 88,620,000
2021 / 2020 | 77,625,000 | 65,629,000
2020 / 2019 | 44,138,000 | 37,169,000
2019 / 2018 | 2,460,000 | 2,727,000
2018 / 2017 | 2,886,000 | 477,000
Prior | 1,435,000 | 1,193,000
Revolving Loans | 2,560,000 | 1,143,000
Total Loans | 158,481,000 | 196,958,000
Construction | Special Mention [Member] |  |
Loans by risk rating |  |
2021 / 2020 | 1,465,000 | 2,138,000
2020 / 2019 | 5,181,000 | 4,932,000
2019 / 2018 | 10,226,000 |
Total Loans | 16,872,000 | 7,070,000
Construction | Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 1,232,000 | 160,000
2019 / 2018 | 115,000 | 1,944,000
Total Loans | 1,347,000 | 2,104,000
Residential real estate - Investor |  |
Loans by risk rating |  |
2022 / 2021 | 13,656,000 | 13,492,000
2021 / 2020 | 10,482,000 | 9,902,000
2020 / 2019 | 7,079,000 | 13,084,000
2019 / 2018 | 10,007,000 | 6,589,000
2018 / 2017 | 5,435,000 | 7,444,000
Prior | 11,707,000 | 11,020,000
Revolving Loans | 1,214,000 | 1,868,000
Total Loans | 59,580,000 | 63,399,000
Residential real estate - Investor | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 13,481,000 | 13,371,000
2021 / 2020 | 10,482,000 | 9,758,000
2020 / 2019 | 7,079,000 | 13,084,000
2019 / 2018 | 9,508,000 | 6,392,000
2018 / 2017 | 5,246,000 | 7,059,000
Prior | 11,285,000 | 10,602,000
Revolving Loans | 1,214,000 | 1,868,000
Total Loans | 58,295,000 | 62,134,000
Residential real estate - Investor | Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 175,000 | 121,000
2021 / 2020 |  | 144,000
2019 / 2018 | 499,000 | 197,000
2018 / 2017 | 189,000 | 385,000
Prior | 422,000 | 418,000
Total Loans | 1,285,000 | 1,265,000
Residential real estate - Owner occupied |  |
Loans by risk rating |  |
2022 / 2021 | 36,688,000 | 48,990,000
2021 / 2020 | 46,296,000 | 32,095,000
2020 / 2019 | 29,402,000 | 20,996,000
2019 / 2018 | 17,132,000 | 14,523,000
2018 / 2017 | 12,553,000 | 30,738,000
Prior | 77,333,000 | 63,854,000
Revolving Loans | 1,565,000 | 2,052,000
Total Loans | 220,969,000 | 213,248,000
Residential real estate - Owner occupied | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 36,688,000 | 48,009,000
2021 / 2020 | 45,430,000 | 31,912,000
2020 / 2019 | 29,163,000 | 20,990,000
2019 / 2018 | 16,407,000 | 13,304,000
2018 / 2017 | 12,421,000 | 30,562,000
Prior | 74,772,000 | 60,661,000
Revolving Loans | 1,565,000 | 2,052,000
Total Loans | 216,446,000 | 207,490,000
Residential real estate - Owner occupied | Special Mention [Member] |  |
Loans by risk rating |  |
2022 / 2021 |  | 659,000
2021 / 2020 | 594,000 |
Total Loans | 594,000 | 659,000
Residential real estate - Owner occupied | Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 |  | 322,000
2021 / 2020 | 272,000 | 183,000
2020 / 2019 | 239,000 | 6,000
2019 / 2018 | 725,000 | 1,219,000
2018 / 2017 | 132,000 | 176,000
Prior | 2,561,000 | 3,193,000
Total Loans | 3,929,000 | 5,099,000
Multifamily |  |
Loans by risk rating |  |
2022 / 2021 | 72,925,000 | 109,608,000
2021 / 2020 | 108,581,000 | 71,748,000
2020 / 2019 | 53,862,000 | 46,193,000
2019 / 2018 | 22,396,000 | 62,733,000
2018 / 2017 | 57,019,000 | 11,701,000
Prior | 7,817,000 | 7,117,000
Revolving Loans | 101,000 | 64,000
Revolving Loans Converted To Term Loans | 155,000 |
Total Loans | 322,856,000 | 309,164,000
Multifamily | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 71,830,000 | 109,175,000
2021 / 2020 | 108,581,000 | 71,748,000
2020 / 2019 | 53,862,000 | 39,293,000
2019 / 2018 | 15,559,000 | 61,190,000
2018 / 2017 | 56,411,000 | 11,399,000
Prior | 7,538,000 | 7,117,000
Revolving Loans | 101,000 | 64,000
Revolving Loans Converted To Term Loans | 155,000 |
Total Loans | 314,037,000 | 299,986,000
Multifamily | Special Mention [Member] |  |
Loans by risk rating |  |
2020 / 2019 |  | 6,900,000
2019 / 2018 | 6,837,000 |
Total Loans | 6,837,000 | 6,900,000
Multifamily | Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 1,095,000 | 433,000
2019 / 2018 |  | 1,543,000
2018 / 2017 | 608,000 | 302,000
Prior | 279,000 |
Total Loans | 1,982,000 | 2,278,000
HELOC |  |
Loans by risk rating |  |
2022 / 2021 | 1,972,000 | 907,000
2021 / 2020 | 517,000 | 2,091,000
2020 / 2019 | 1,512,000 | 2,131,000
2019 / 2018 | 1,728,000 | 822,000
2018 / 2017 | 731,000 | 1,679,000
Prior | 2,826,000 | 12,691,000
Revolving Loans | 106,822,000 | 105,969,000
Total Loans | 116,108,000 | 126,290,000
HELOC | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 1,909,000 | 907,000
2021 / 2020 | 517,000 | 2,091,000
2020 / 2019 | 1,512,000 | 2,131,000
2019 / 2018 | 1,728,000 | 805,000
2018 / 2017 | 661,000 | 1,667,000
Prior | 2,616,000 | 12,315,000
Revolving Loans | 104,776,000 | 104,843,000
Total Loans | 113,719,000 | 124,759,000
HELOC | Special Mention [Member] |  |
Loans by risk rating |  |
Revolving Loans | 111,000 | 108,000
Total Loans | 111,000 | 108,000
HELOC | Substandard [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 63,000 |
2019 / 2018 |  | 17,000
2018 / 2017 | 70,000 | 12,000
Prior | 210,000 | 376,000
Revolving Loans | 1,935,000 | 1,018,000
Total Loans | 2,278,000 | 1,423,000
Other |  |
Loans by risk rating |  |
2022 / 2021 | 2,892,000 | 8,659,000
2021 / 2020 | 3,102,000 | 1,102,000
2020 / 2019 | 503,000 | 437,000
2019 / 2018 | 166,000 | 261,000
2018 / 2017 | 57,000 | 1,414,000
Prior | 122,000 | 4,214,000
Revolving Loans | 7,734,000 | 7,206,000
Total Loans | 14,576,000 | 23,293,000
Other | Pass [Member] |  |
Loans by risk rating |  |
2022 / 2021 | 2,892,000 | 8,659,000
2021 / 2020 | 3,102,000 | 1,099,000
2020 / 2019 | 501,000 | 437,000
2019 / 2018 | 166,000 | 254,000
2018 / 2017 | 57,000 | 1,414,000
Prior | 122,000 | 4,214,000
Revolving Loans | 7,734,000 | 7,206,000
Total Loans | 14,574,000 | 23,283,000
Other | Substandard [Member] |  |
Loans by risk rating |  |
2021 / 2020 |  | 3,000
2020 / 2019 | 2,000 |
2019 / 2018 |  | 7,000
Total Loans | $ 2,000 | $ 10,000

X
- Definition Amortized cost of financing receivable and net investment in lease originated in current fiscal year. + References No definition available. + Details
Name: | osbc_FinancingReceivableAndNetInvestmentInLeaseOriginatedCurrentFiscalYear
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable and net investment in lease originated five or more years before latest fiscal year. + References No definition available. + Details
Name: | osbc_FinancingReceivableAndNetInvestmentInLeaseOriginatedFiveOrMoreYearsBeforeLatestFiscalYear
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable and net investment in lease originated four years before latest fiscal year. + References No definition available. + Details
Name: | osbc_FinancingReceivableAndNetInvestmentInLeaseOriginatedFourYearsBeforeLatestFiscalYear
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable and net investment in lease originated in fiscal year before latest fiscal year. + References No definition available. + Details
Name: | osbc_FinancingReceivableAndNetInvestmentInLeaseOriginatedInFiscalYearBeforeLatestFiscalYear
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable and net investment in lease originated three years before latest fiscal year. + References No definition available. + Details
Name: | osbc_FinancingReceivableAndNetInvestmentInLeaseOriginatedThreeYearsBeforeLatestFiscalYear
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable and net investment in lease originated two years before latest fiscal year. + References No definition available. + Details
Name: | osbc_FinancingReceivableAndNetInvestmentInLeaseOriginatedTwoYearsBeforeLatestFiscalYear
Namespace Prefix: | osbc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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 The amount Financing Receivables that are converted from revolving to term loans. + References No definition available. + Details
Name: | osbc_FinancingReceivableRevolvingLoansConvertedToTermLoans
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 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 Amortized cost 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 https://asc.fasb.org/extlink&oid=124255953&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 https://asc.fasb.org/extlink&oid=124267575&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 https://asc.fasb.org/extlink&oid=124259787&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 https://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524 + Details
Name: | us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
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 https://asc.fasb.org/extlink&oid=123577603&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_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
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_FinancingReceivablePortfolioSegmentAxis=osbc_RealEstateOwnerOccupiedMember
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_FinancingReceivablePortfolioSegmentAxis=us-gaap_HomeEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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