Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Oct. 15, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	0-6233
Entity Incorporation, State or Country Code	IN
Entity Tax Identification Number	35-1068133
Entity Address, Address Line One	100 North Michigan Street
Entity Address, City or Town	South Bend,
Entity Address, State or Province	IN
Entity Address, Postal Zip Code	46601
City Area Code	574
Local Phone Number	235-2000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock - without par value
Trading Symbol	SRCE
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		24,797,533
Entity Registrant Name	1st Source Corp
Entity Central Index Key	0000034782
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false