1st Source Corporation (Parent Company Only) Financial Information (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of premises and equipment	$ 5,093	$ 5,673	$ 5,786
Amortization of right of use assets	3,095	2,842	3,046
Stock-based compensation	4,214	3,293	2,765
Other	279	940	1,734
Investing activities:
Net change in partnership investments	24,897	54,981	33,840
Financing activities:
Proceeds from issuance of long-term debt and mandatorily redeemable securities	0	10,000	0
Payments on long-term debt and mandatorily redeemable securities	(13,460)	(2,905)	(2,695)
Stock issued under stock purchase plans	90	39	49
Acquisition of treasury stock	(33,136)	(6,415)	(15,085)
Cash dividends paid on common stock	(31,340)	(29,764)	(29,021)
Parent Company
1st Source Corporation (Parent Company Only) Financial Information
Net income	118,557	81,461	92,015
Adjustments to reconcile net income to net cash provided by operating activities:
Equity (undistributed) distributed in excess of income of subsidiaries	(76,493)	(42,178)	(49,678)
Depreciation of premises and equipment	1	2	2
Amortization of right of use assets	1,346	1,107	1,350
Stock-based compensation	102	94	78
Realized/unrealized investment securities and other investment (gains) losses	(342)	44	(109)
Other	1,556	(103)	533
Net change in operating activities	44,727	40,427	44,191
Investing activities:
Net change in partnership investments	(74)	(182)	(260)
Payments to Acquire Businesses and Interest in Affiliates	0	0	(325)
Net change in investing activities	(74)	(182)	(585)
Financing activities:
Net change in commercial paper	(800)	774	(332)
Proceeds from issuance of long-term debt and mandatorily redeemable securities	1,738	1,640	1,611
Payments on long-term debt and mandatorily redeemable securities	(2,427)	(2,268)	(2,068)
Stock issued under stock purchase plans	90	39	49
Net proceeds from issuance of treasury stock	2,523	1,706	1,878
Acquisition of treasury stock	(33,136)	(6,415)	(15,085)
Cash dividends paid on common stock	(31,340)	(29,764)	(29,021)
Net change in financing activities	(63,352)	(34,288)	(42,968)
Net change in cash and cash equivalents	(18,699)	5,957	638
Cash and cash equivalents, beginning of year	113,242	107,285	106,647
Cash and cash equivalents, end of year	$ 94,543	$ 113,242	$ 107,285