Regulatory Matters (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013
Total Capital (to Risk-Weighted Assets):
Actual Amount	$ 555,163,000	$ 599,603,000
Actual Ratio (as a percent)	15.57%	15.86%
Minimum Capital Adequacy Amount	285,304,000	302,409,000
Minimum Capital Adequacy Ratio (as a percent)	8.00%	8.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	356,631,000	378,011,000
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	508,582,000	549,441,000
Actual Ratio (as a percent)	14.26%	14.54%
Minimum Capital Adequacy Amount	142,652,000	151,205,000
Minimum Capital Adequacy Ratio (as a percent)	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	213,978,000	226,807,000
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.00%	6.00%
Tier I Capital (to Average Assets):
Actual Amount	508,582,000	549,441,000
Actual Ratio (as a percent)	11.47%	12.08%
Minimum Capital Adequacy Amount	177,299,000	182,008,000
Minimum Capital Adequacy Ratio (as a percent)	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	221,624,000	227,510,000
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	5.00%	5.00%
Average noninterest bearing cash balances with the Federal Reserve Bank	1,620,000
1st Source Bank
Total Capital (to Risk-Weighted Assets):
Actual Amount	535,409,000	566,307,000
Actual Ratio (as a percent)	15.05%	15.01%
Minimum Capital Adequacy Amount	284,611,000	301,783,000
Minimum Capital Adequacy Ratio (as a percent)	8.00%	8.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	355,763,000	377,229,000
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	490,077,000	518,230,000
Actual Ratio (as a percent)	13.78%	13.74%
Minimum Capital Adequacy Amount	142,305,000	150,892,000
Minimum Capital Adequacy Ratio (as a percent)	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	213,458,000	226,338,000
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	6.00%	6.00%
Tier I Capital (to Average Assets):
Actual Amount	490,077,000	518,230,000
Actual Ratio (as a percent)	11.08%	11.41%
Minimum Capital Adequacy Amount	176,928,000	181,726,000
Minimum Capital Adequacy Ratio (as a percent)	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 221,160,000	$ 227,157,000
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	5.00%	5.00%