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Regulatory & Capital Matters (Details) | 6 Months Ended |
--- | --- | ---
Jun. 30, 2018 | Dec. 31, 2017
Regulatory & Capital Matters |  |
Tier 1 capital leverage ratio (as a percent) | 9.37% | 10.08%
Risk-based capital ratio (as a percent) | 11.87% | 12.93%
Old Second National Bank |  |
Regulatory & Capital Matters |  |
Tier 1 capital leverage ratio (as a percent) | 10.75% | 10.79%
Risk-based capital ratio (as a percent) | 13.51% | 13.78%
Tier One leverage ratio, basis point increase (as a percent) | 0.04% |
Risk-based capital ratio, basis point decrease (as a percent) | 0.27% |
Minimum | Old Second National Bank |  |
Regulatory & Capital Matters |  |
Tier 1 capital leverage ratio, board-designated threshold | 8.00% |
Total Capital Ratio, board-designated threshold (as a percent) | 12.00% |

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- Definition Total Capital divided by risk weighted assets as defined in the regulations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826 + Details
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