1st Source Corporation (Parent Company Only) Financial Information (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 66,190	$ 80,052	$ 83,934	$ 114,327
Investment securities, available-for-sale (amortized cost of $1,218 at December 31, 2014 and 2013, respectively)	791,118	832,700
Other investments	20,801	22,400
Trading account securities	205	192
Other assets	124,692	121,644
Total assets	4,829,958	4,722,826
LIABILITIES AND SHAREHOLDERS' EQUITY
Other liabilities	51,807	52,568
Long-term debt and mandatorily redeemable securities	56,232	58,335
Subordinated notes	58,764	58,764
Total liabilities	4,215,485	4,137,448
Shareholders' equity	614,473	585,378	558,655	523,918
Total liabilities and shareholders' equity	4,829,958	4,722,826
Available-for-sale Securities, Amortized Cost	776,057	822,163
Parent
ASSETS
Cash and cash equivalents	51,725	54,348	32,603	24,415
Investment securities, available-for-sale (amortized cost of $1,218 at December 31, 2014 and 2013, respectively)	6,240	5,636
Other investments	1,470	1,470
Trading account securities	205	192
Other assets	6,356	5,475
Total assets	706,696	677,690
LIABILITIES AND SHAREHOLDERS' EQUITY
Commercial paper borrowings	12,168	12,351
Other liabilities	3,641	5,373
Long-term debt and mandatorily redeemable securities	17,650	15,824
Subordinated notes	58,764	58,764
Total liabilities	92,223	92,312
Shareholders' equity	614,473	585,378
Total liabilities and shareholders' equity	706,696	677,690
Available-for-sale Securities, Amortized Cost	1,218	1,218
Parent | Bank subsidiaries
ASSETS
Short-term investments	500	500
Investments in subsidiary	639,035	607,695
Parent | Non-bank subsidiaries
ASSETS
Investments in subsidiary	$ 1,165	$ 2,374