Condensed Statements of Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statements, Captions [Line Items]
Net income	$ 7,246	$ 3,484	$ 6,552
Other comprehensive income:
Net unrealized holding gain (loss) on securities available-for-sale	4,782	10,267	(2,600)
Net unrealized gain (loss) on securities available-for-sale for which a portion of an other-than-temporary impairment has been recognized in income	43	(56)	(1,307)
Less: Reclassification adjustment for realized (gains) losses included in net income	(2,831)	(1,855)	894
Net unrealized gain (loss) on derivative used for cash flow hedges	56	(133)	(383)
Net unrealized gain (loss) relating to defined benefit plan	399	(197)	186
Other Comprehensive Income (Loss), before Tax	2,449	8,026	(3,210)
Income tax (expense) benefit related to other comprehensive income	(849)	(2,835)	1,079
Other comprehensive income (loss)	1,600	5,191	(2,131)
Comprehensive income	8,846	8,675	4,421
MutualFirst Financial, Inc.
Condensed Financial Statements, Captions [Line Items]
Net income	7,246	3,484	6,552
Other comprehensive income:
Net unrealized holding gain (loss) on securities available-for-sale	4,782	10,267	(2,600)
Net unrealized gain (loss) on securities available-for-sale for which a portion of an other-than-temporary impairment has been recognized in income	43	(56)	(1,307)
Less: Reclassification adjustment for realized (gains) losses included in net income	(2,831)	(1,855)	894
Net unrealized gain (loss) on derivative used for cash flow hedges	56	(133)	(383)
Net unrealized gain (loss) relating to defined benefit plan	399	(197)	186
Other Comprehensive Income (Loss), before Tax	2,449	8,026	(3,210)
Income tax (expense) benefit related to other comprehensive income	(849)	(2,835)	1,079
Other comprehensive income (loss)	1,600	5,191	(2,131)
Comprehensive income	$ 8,846	$ 8,675	$ 4,421