Regulatory Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Total Capital (to Risk-Weighted Assets):
Actual Amount	$ 676,007	$ 629,023
Actual Ratio (as a percent)	14.97%	15.89%
Minimum Capital Adequacy Amount	$ 361,267	$ 316,704
Minimum Capital Adequacy Ratio (as a percent)	8.00%	8.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 451,584	$ 395,880
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	10.00%	10.00%
Tier I Capital (to Risk-Weighted Assets):
Actual Amount	$ 616,577	$ 576,692
Actual Ratio (as a percent)	13.65%	14.57%
Minimum Capital Adequacy Amount	$ 270,951	$ 158,352
Minimum Capital Adequacy Ratio (as a percent)	6.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 361,267	$ 237,528
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	8.00%	6.00%
Common Equity Tier 1 Capital (to Risk-Weighted Assets):
Actual Amount	$ 559,577
Actual Ratio (as a percent)	12.39%
Minimum Capital Adequacy Amount	$ 203,213
Minimum Capital Adequacy Ratio (as a percent)	4.50%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 293,530
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.50%
Tier I Capital (to Average Assets):
Actual Amount	$ 616,577	$ 576,692
Actual Ratio (as a percent)	12.21%	12.16%
Minimum Capital Adequacy Amount	$ 201,921	$ 189,718
Minimum Capital Adequacy Ratio (as a percent)	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 252,401	$ 237,147
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	5.00%	5.00%
1st Source Bank
Total Capital (to Risk-Weighted Assets):
Actual Amount	$ 636,592	$ 598,038
Actual Ratio (as a percent)	14.13%	15.15%
Minimum Capital Adequacy Amount	$ 360,402	$ 315,886
Minimum Capital Adequacy Ratio (as a percent)	8.00%	8.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 450,502	$ 394,857
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	10.00%	10.00%
Tier I Capital (to Risk-Weighted Assets):
Actual Amount	$ 579,833	$ 548,094
Actual Ratio (as a percent)	12.87%	13.88%
Minimum Capital Adequacy Amount	$ 270,301	$ 157,943
Minimum Capital Adequacy Ratio (as a percent)	6.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 360,402	$ 236,914
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	8.00%	6.00%
Common Equity Tier 1 Capital (to Risk-Weighted Assets):
Actual Amount	$ 579,833
Actual Ratio (as a percent)	12.87%
Minimum Capital Adequacy Amount	$ 202,726
Minimum Capital Adequacy Ratio (as a percent)	4.50%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 292,826
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.50%
Tier I Capital (to Average Assets):
Actual Amount	$ 579,833	$ 548,094
Actual Ratio (as a percent)	11.50%	11.57%
Minimum Capital Adequacy Amount	$ 201,701	$ 189,412
Minimum Capital Adequacy Ratio (as a percent)	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 252,126	$ 236,765
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	5.00%	5.00%