Employee Benefit Plans	12 Months Ended
Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans The 1st Source Corporation Employee Stock Ownership and Profit Sharing Plan (as amended, the “Plan”) includes an employee stock ownership component, which is designed to invest in and hold 1st Source common stock, and a 401(k) plan component, which holds all Plan assets not invested in 1st Source common stock. The Plan encourages diversification of investments with opportunities to change investment elections and contribution levels. Employees are eligible to participate in the Plan the first of the month following 90 days of employment. The Company matches dollar for dollar on the first 4% of deferred compensation, plus 50 cents on the dollar of the next 2% deferrals. The Company will also contribute to the Plan an amount designated as a fixed 2% employer contribution. The amount of fixed contribution is equal to two percent of the participant’s eligible compensation. Additionally, each year the Company may, in its sole discretion, make a discretionary profit sharing contribution. As of December 31, 2017 and 2016, there were 1,126,939 and 1,252,417 shares, respectively, of 1st Source Corporation common stock held in relation to employee benefit plans. The Company contributions are allocated among the participants on the basis of compensation. Each participant’s account is credited with cash and/or shares of 1st Source common stock based on that participant’s compensation earned during the year. After completing 5 years of service in which they worked at least 1,000 hours per year, a participant will be completely vested in the Company’s contribution. An employee is always 100% vested in their deferral. Plan participants are entitled to receive distributions from their Plan accounts upon termination of service, retirement, or death. Contribution expense for the years ended December 31, 2017, 2016, and 2015, amounted to $4.88 million, $4.71 million, and $4.57 million, respectively. In addition to the 1st Source Corporation Employee Stock Ownership and Profit Sharing Plan, the Company provides a limited health care and life insurance benefit for some of its retired employees. Effective March 31, 2009, the Company amended the plan so that no new retirees would be covered by the plan. The amendment will have no effect on the coverage for retirees covered at the time of the amendment. Prior to amendment, all full-time employees became eligible for these retiree benefits upon reaching age 55 with 20 years of credited service. The retiree medical plan pays a stated percentage of eligible medical expenses reduced by any deductibles and payments made by government programs and other group coverage. The lifetime maximum benefit payable under the medical plan is $15,000 and for life insurance is $3,000. The Company’s net periodic post retirement benefit (recovery) cost recognized in Salaries and Employee Benefits in the Statements of Income for the years ended December 31, 2017, 2016 and 2015, amounted to $(0.01) million, $(0.01) million, and $(0.02) million, respectively. The accrued post retirement benefit cost was not material at December 31, 2017, 2016, and 2015.

Employee Benefit Plans

The 1st Source Corporation Employee Stock Ownership and Profit Sharing Plan (as amended, the “Plan”) includes an employee stock ownership component, which is designed to invest in and hold 1st Source common stock, and a 401(k) plan component, which holds all Plan assets not invested in 1st Source common stock. The Plan encourages diversification of investments with opportunities to change investment elections and contribution levels.

Employees are eligible to participate in the Plan the first of the month following 90 days of employment. The Company matches dollar for dollar on the first 4% of deferred compensation, plus 50 cents on the dollar of the next 2% deferrals. The Company will also contribute to the Plan an amount designated as a fixed 2% employer contribution. The amount of fixed contribution is equal to two percent of the participant’s eligible compensation. Additionally, each year the Company may, in its sole discretion, make a discretionary profit sharing contribution. As of December 31, 2017 and 2016, there were 1,126,939 and 1,252,417 shares, respectively, of 1st Source Corporation common stock held in relation to employee benefit plans.

The Company contributions are allocated among the participants on the basis of compensation. Each participant’s account is credited with cash and/or shares of 1st Source common stock based on that participant’s compensation earned during the year. After completing 5 years of service in which they worked at least 1,000 hours per year, a participant will be completely vested in the Company’s contribution. An employee is always 100% vested in their deferral. Plan participants are entitled to receive distributions from their Plan accounts upon termination of service, retirement, or death.

Contribution expense for the years ended December 31, 2017, 2016, and 2015, amounted to $4.88 million, $4.71 million, and $4.57 million, respectively.

In addition to the 1st Source Corporation Employee Stock Ownership and Profit Sharing Plan, the Company provides a limited health care and life insurance benefit for some of its retired employees. Effective March 31, 2009, the Company amended the plan so that no new retirees would be covered by the plan. The amendment will have no effect on the coverage for retirees covered at the time of the amendment. Prior to amendment, all full-time employees became eligible for these retiree benefits upon reaching age 55 with 20 years of credited service. The retiree medical plan pays a stated percentage of eligible medical expenses reduced by any deductibles and payments made by government programs and other group coverage. The lifetime maximum benefit payable under the medical plan is $15,000 and for life insurance is $3,000.

The Company’s net periodic post retirement benefit (recovery) cost recognized in Salaries and Employee Benefits in the Statements of Income for the years ended December 31, 2017, 2016 and 2015, amounted to $(0.01) million, $(0.01) million, and $(0.02) million, respectively. The accrued post retirement benefit cost was not material at December 31, 2017, 2016, and 2015.