Employee Benefit Plans	12 Months Ended
Dec. 31, 2017
Employee Benefit Plans
Employee Benefit Plans	Note 23: Employee Benefit Plans Old Second Bancorp, Inc. Employees 401(k) Savings Plan and Trust The Company sponsors a qualified, tax-exempt defined contribution plan (the “Plan”) qualifying under section 401(k) of the Internal Revenue Code. Virtually all employees are eligible to participate after meeting certain age and service requirements. Eligible employees are permitted to contribute up to a dollar limit set by law of their compensation to the Plan. For the years ended December 31, 2017, 2016 and 2015, a discretionary match equal to 100% of the first 3% of the participant’s compensation was contributed to participants of the Plan. Participants are 100% vested in the discretionary matching contributions. Participants can choose between several different investment options under the Plan, including shares of the Company’s common stock. An additional component of the Plan arrangement allows for the Company to make annual discretionary contributions under a profit sharing portion based on the Company’s profitability in a given year, and on each participant’s annual compensation. The Company elected not to make a discretionary profit sharing contribution for the years end December 31, 2017, 2016 and 2015. The total expense relating to the Plan was approximately $698,000, $464,000 and $477,000 in 2017, 2016 and 2015, respectively. Old Second Bancorp, Inc. Voluntary Deferred Compensation Plan for Executives The Company sponsors an executive deferred compensation plan, which is a means by which certain executives may voluntarily defer a portion of their salary or bonus. This plan is an unfunded, nonqualified deferred compensation arrangement. Company obligations under this arrangement as of December 31, 2017, 2016 and 2015 were $1.7 million, $1.6 million and $1.9 million, respectively, and are included in other liabilities.

Note 23: Employee Benefit Plans

Old Second Bancorp, Inc. Employees 401(k) Savings Plan and Trust

The Company sponsors a qualified, tax-exempt defined contribution plan (the “Plan”) qualifying under section 401(k) of the Internal Revenue Code. Virtually all employees are eligible to participate after meeting certain age and service requirements. Eligible employees are permitted to contribute up to a dollar limit set by law of their compensation to the Plan. For the years ended December 31, 2017, 2016 and 2015, a discretionary match equal to 100% of the first 3% of the participant’s compensation was contributed to participants of the Plan. Participants are 100% vested in the discretionary matching contributions. Participants can choose between several different investment options under the Plan, including shares of the Company’s common stock. An additional component of the Plan arrangement allows for the Company to make annual discretionary contributions under a profit sharing portion based on the Company’s profitability in a given year, and on each participant’s annual compensation. The Company elected not to make a discretionary profit sharing contribution for the years end December 31, 2017, 2016 and 2015.

The total expense relating to the Plan was approximately $698,000, $464,000 and $477,000 in 2017, 2016 and 2015, respectively.

Old Second Bancorp, Inc. Voluntary Deferred Compensation Plan for Executives

The Company sponsors an executive deferred compensation plan, which is a means by which certain executives may voluntarily defer a portion of their salary or bonus. This plan is an unfunded, nonqualified deferred compensation arrangement. Company obligations under this arrangement as of December 31, 2017, 2016 and 2015 were $1.7 million, $1.6 million and $1.9 million, respectively, and are included in other liabilities.