Regulatory & Capital Matters (Details)	Dec. 31, 2015	Dec. 31, 2014
Regulatory & Capital Matters
Tier 1 capital leverage ratio (as a percent)	8.69%	9.93%
Total capital ratio (as a percent)	15.56%	17.68%
Old Second National Bank
Regulatory & Capital Matters
Tier 1 capital leverage ratio (as a percent)	9.94%	12.02%
Total capital ratio (as a percent)	15.23%	18.73%