XML 119 R103.htm IDEA: XBRL DOCUMENT v3.6.0.2
Employee Benefit Plans (Details) - USD ($)
$ in Thousands
12 Months Ended 36 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2016
Employee Benefit Plans        
Company obligations under Voluntary Deferred Compensation Plan for Executives $ 1,700 $ 1,600 $ 1,900 $ 1,700
Old Second Bancorp Inc Employees 401(k) Savings Plan and Trust        
Employee Benefit Plans        
Company's discretionary matching contributions to the Plan (as a percent) 100.00% 100.00% 100.00%  
Percentage of compensation contributed to the Plan matched by employer 3.00% 3.00% 2.00%  
Participants vesting as percentage of discretionary matching contributions       100.00%
Expense relating to the 401(k) plan $ 698 $ 464 $ 477