Condensed Financial Information (Parent Company Only) (Condensed Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net income	$ 12,315	$ 13,241	$ 12,262
Other Comprehensive Income (Loss)
Net unrealized holding gain (loss) on securities available for sale	3,112	(3,258)	(1,174)
Less: Reclassification adjustment for realized gains included in net included in net income	(708)	(1,023)	(436)
Net unrealized gain (loss) on derivative used for cash flow hedges		1	108
Net unrealized gain (loss) relating to defined benefit plan	(20)	62	77
Other Comprehensive Income (Loss), before Tax	2,384	(4,218)	(1,425)
Income tax benefit (expense) related to other comprehensive income	(749)	1,474	537
Other comprehensive income (loss)	1,635	(2,744)	(888)
Comprehensive income	13,950	10,497	11,374
MutualFirst Financial, Inc.
Condensed Financial Statements, Captions [Line Items]
Net income	12,315	13,241	12,262
Other Comprehensive Income (Loss)
Net unrealized gain on securities available for sale for which a portion of an other-than-temporary impairment has been recognized in income	3,112	(3,258)	(1,174)
Less: Reclassification adjustment for realized gains included in net included in net income	(708)	(1,023)	(436)
Net unrealized gain (loss) on derivative used for cash flow hedges		1	108
Net unrealized gain (loss) relating to defined benefit plan	(20)	62	77
Other Comprehensive Income (Loss), before Tax	2,384	(4,218)	(1,425)
Income tax benefit (expense) related to other comprehensive income	(749)	1,474	537
Other comprehensive income (loss)	1,635	(2,744)	(888)
Comprehensive income	$ 13,950	$ 10,497	$ 11,374