1st Source Corporation (Parent Company Only) Financial Information (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income:
Rental income from subsidiaries	$ 25,863	$ 22,302	$ 17,156
Other	12,081	12,319	12,051
Expenses:
Interest on subordinated notes	4,220	4,220	4,220
Interest on long-term debt and mandatorily redeemable securities	2,089	1,970	2,108
Interest on commercial paper and other short-term borrowings	525	484	541
Other	5,856	6,976	7,521
Income before income taxes	89,126	88,563	84,443
Income tax benefit	(31,340)	(31,077)	(26,374)
Net income	57,786	57,486	58,069
Comprehensive income	52,575	54,634	60,895
Parent
Income:
Rental income from subsidiaries	2,363	2,342	2,314
Other	444	426	408
Investment securities and other investment gains (losses)	3,901	26	(370)
Total income	42,772	38,858	36,162
Expenses:
Interest on subordinated notes	4,220	4,220	4,220
Interest on long-term debt and mandatorily redeemable securities	1,454	1,375	1,475
Interest on commercial paper and other short-term borrowings	20	30	36
Rent	1,739	1,737	1,713
Other	1,179	351	2,553
Total expenses	8,612	7,713	9,997
Income before income taxes	34,160	31,145	26,165
Income tax benefit	741	1,721	2,722
Income before equity in undistributed income of subsidiaries	34,901	32,866	28,887
Equity in undistributed income of subsidiaries	22,885	24,620	29,182
Net income	57,786	57,486	58,069
Comprehensive income	52,575	54,634	60,895
Parent | Bank subsidiaries
Income:
Dividends from bank subsidiary	36,064	36,064	33,810
Expenses:
Equity in undistributed income of subsidiaries	22,569	24,289	28,891
Parent | Non-bank subsidiaries
Expenses:
Equity in undistributed income of subsidiaries	$ 316	$ 331	$ 291