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Regulatory & Capital Matters (Details) | 6 Months Ended |
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Jun. 30, 2017 | Dec. 31, 2016
Regulatory & Capital Matters |  |
Tier 1 capital leverage ratio (as a percent) | 9.09% | 8.90%
Risk-based capital ratio (as a percent) | 12.14% | 12.29%
Old Second National Bank |  |
Regulatory & Capital Matters |  |
Tier 1 capital leverage ratio (as a percent) | 10.23% | 10.24%
Risk-based capital ratio (as a percent) | 13.30% | 13.45%
Tier One leverage ratio, basis point increase (as a percent) | 0.01% |
Risk-based capital ratio, basis point decrease (as a percent) | 0.15% |
Old Second National Bank | Minimum |  |
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=35709795&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=35709795&loc=SL5958568-112826 + Details
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