Regulatory Matters (Details) $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Total Capital (to Risk-Weighted Assets):
Actual Amount	$ 1,248,905	$ 1,137,984
Actual Ratio (as a percent)	0.1625	0.1610
Minimum Capital Adequacy Amount	$ 614,880	$ 565,314
Minimum Capital Adequacy Ratio (as a percent)	0.0800	0.0800
Minimum Capital Adequacy with Capital Buffer Amount	$ 807,031	$ 741,975
Minimum Capital Adequacy with Capital Buffer Ratio (as a percent)	0.1050	0.1050
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 768,601	$ 706,643
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	0.1000	0.1000
Tier I Capital (to Risk-Weighted Assets):
Actual Amount	$ 1,152,093	$ 1,048,955
Actual Ratio (as a percent)	0.1499	0.1484
Minimum Capital Adequacy Amount	$ 461,160	$ 423,986
Minimum Capital Adequacy Ratio (as a percent)	0.0600	0.0600
Minimum Capital Adequacy with Capital Buffer Amount	$ 653,311	$ 600,647
Minimum Capital Adequacy with Capital Buffer Ratio (as a percent)	0.0850	0.0850
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 614,880	$ 565,314
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	0.0800	0.0800
Common Equity Tier 1 Capital (to Risk-Weighted Assets):
Actual Amount	$ 1,016,398	$ 932,257
Actual Ratio (as a percent)	0.1322	0.1319
Minimum Capital Adequacy Amount	$ 345,870	$ 317,989
Minimum Capital Adequacy Ratio (as a percent)	0.0450	0.0450
Minimum Capital Adequacy with Capital Buffer Amount	$ 538,020	$ 494,650
Minimum Capital Adequacy with Capital Buffer Ratio (as a percent)	0.0700	0.0700
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 499,590	$ 459,318
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	0.0650	0.0650
Tier I Capital (to Average Assets):
Actual Amount	$ 1,152,093	$ 1,048,955
Actual Ratio (as a percent)	0.1326	0.1263
Minimum Capital Adequacy Amount	$ 347,512	$ 332,287
Minimum Capital Adequacy Ratio (as a percent)	0.0400	0.0400
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 434,390	$ 415,359
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	0.0500	0.0500
1st Source Bank
Total Capital (to Risk-Weighted Assets):
Actual Amount	$ 1,168,672	$ 1,060,292
Actual Ratio (as a percent)	0.1521	0.1501
Minimum Capital Adequacy Amount	$ 614,547	$ 565,119
Minimum Capital Adequacy Ratio (as a percent)	0.0800	0.0800
Minimum Capital Adequacy with Capital Buffer Amount	$ 806,593	$ 741,718
Minimum Capital Adequacy with Capital Buffer Ratio (as a percent)	0.1050	0.1050
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 768,184	$ 706,398
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	0.1000	0.1000
Tier I Capital (to Risk-Weighted Assets):
Actual Amount	$ 1,071,912	$ 971,294
Actual Ratio (as a percent)	0.1395	0.1375
Minimum Capital Adequacy Amount	$ 460,910	$ 423,839
Minimum Capital Adequacy Ratio (as a percent)	0.0600	0.0600
Minimum Capital Adequacy with Capital Buffer Amount	$ 652,956	$ 600,439
Minimum Capital Adequacy with Capital Buffer Ratio (as a percent)	0.0850	0.0850
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 614,547	$ 565,119
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	0.0800	0.0800
Common Equity Tier 1 Capital (to Risk-Weighted Assets):
Actual Amount	$ 993,217	$ 911,596
Actual Ratio (as a percent)	0.1293	0.1290
Minimum Capital Adequacy Amount	$ 345,683	$ 317,879
Minimum Capital Adequacy Ratio (as a percent)	0.0450	0.0450
Minimum Capital Adequacy with Capital Buffer Amount	$ 537,729	$ 494,479
Minimum Capital Adequacy with Capital Buffer Ratio (as a percent)	0.0700	0.0700
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 499,319	$ 459,159
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	0.0650	0.0650
Tier I Capital (to Average Assets):
Actual Amount	$ 1,071,912	$ 971,294
Actual Ratio (as a percent)	0.1234	0.1170
Minimum Capital Adequacy Amount	$ 347,397	$ 332,125
Minimum Capital Adequacy Ratio (as a percent)	0.0400	0.0400
To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 434,246	$ 415,156
To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio (as a percent)	0.0500	0.0500