Condensed Financial Information (Parent Company Only) (Condensed Statements of Income) (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income
Interest income from Bank													$ 130	$ 76	$ 14
Total interest and dividend income	$ 15,081	$ 15,026	$ 14,652	$ 14,109	$ 13,943	$ 13,567	$ 13,258	$ 13,034	$ 13,313	$ 13,049	$ 12,731	$ 12,683	58,868	53,802	51,776
Expenses	2,888	2,762	2,565	2,396	2,374	2,330	2,271	2,272	2,214	2,233	2,191	2,165	10,611	9,247	8,803
Income tax benefit													6,793	4,386	4,578
Net Income													12,315	13,241	12,262
Net Income Available to Common Shareholders	$ 1,460	$ 3,751	$ 3,898	$ 3,206	$ 3,237	$ 3,482	$ 4,157	$ 2,365	$ 3,338	$ 3,225	$ 3,218	$ 2,481	12,315	13,241	12,262
MutualFirst Financial, Inc.
Income
Interest income from Bank															1
Dividends from subsidiaries													15,100	12,000	3,600
Total interest and dividend income													15,100	12,000	3,601
Expenses													1,041	976	1,182
Income before income tax and equity in undistributed income of subsidiaries													14,059	11,024	2,419
Income tax benefit													(495)	(399)	(591)
Income before equity in undistributed income (distributions in excess of income) of subsidiaries													14,554	11,423	3,010
Equity in undistributed income (distributions in excess of income) of subsidiaries													(2,239)	1,818	9,252
Net Income													12,315	13,241	12,262
Net Income Available to Common Shareholders													$ 12,315	$ 13,241	$ 12,262