Regulatory Capital (Actual Capital Amounts and Ratios) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Compliance with Regulatory Capital Requirements for Mortgage Companies [Line Items]
Description of regulatory requirements, capital adequacy purposes	The minimum capital requirements exclude the capital conservation buffer required to avoid limitations on capital distributions, including dividend payments and certain discretionary bonus payments to executive officers. The capital conservation buffer is being phased in annually, which started January 1, 2016, at the rate of 0.625% per year until fully phased in during 2019. The capital conservation buffer was 1.25% at December 31, 2017.
Capital coversion percentage	1.25%
MutualFirst Consolidated
Compliance with Regulatory Capital Requirements for Mortgage Companies [Line Items]
Leverage Capital Level, Actual Capital Levels Amount	$ 148,135	$ 138,971
Common Equity Tier 1 Capital Level Amount	144,764	136,606
Total Risk-Based Capital Level, Actual Capital Levels Amount	160,522	151,353
Tier 1 Risk-Based Capital Level, Actual Capital Levels Amount	$ 148,135	$ 138,971
Leverage Capital Level, Actual Capital Levels Ratio	9.40%	9.00%
Common Equity Tier 1 Capital level, Actual Capital Levels Ratio	12.20%	11.90%
Total Risk-Based Capital Level, Actual Capital Levels Ratio	13.50%	13.20%
Tier 1 Risk-Based Capital Level, Actual Capital Levels Ratio	12.50%	12.10%
Leverage Capital Level, Minimum Regulatory Capital Ratios Amount	$ 63,293	$ 61,914
Common Equity Tier 1 Risk-Based Capital Level, Minimum Regulatory Capital Ratios Amount	53,249	51,729
Total Risk-Based Capital Level, Minimum Regulatory Capital Ratios Amount	94,984	91,963
Tier 1 Risk-Based Capital Level, Minimum Regulatory Capital Ratios Amount	$ 71,238	$ 68,973
Leverage Capital Level, Minimum Regulatory Capital Ratios	4.00%	4.00%
Common Equity Tier 1 Risk-Based Capital Level, Minimum Regulatory Catial Ratios	4.50%	4.50%
Total Risk-Based Capital Level, Minimum Regulatory Capital Ratios	8.00%	8.00%
Tier 1 Risk-Based Capital Level, Minimum Regulatory Capital Ratios	6.00%	6.00%
Tier 1 Capital to Average Total Assets	$ 1,600,000	$ 1,500,000
Risk-Weighted Regulatory Capital Assets	1,200,000	1,100,000
MutualBank
Compliance with Regulatory Capital Requirements for Mortgage Companies [Line Items]
Leverage Capital Level, Actual Capital Levels Amount	133,515	136,301
Common Equity Tier 1 Capital Level Amount	133,515	136,301
Total Risk-Based Capital Level, Actual Capital Levels Amount	145,902	148,683
Tier 1 Risk-Based Capital Level, Actual Capital Levels Amount	$ 133,515	$ 136,301
Leverage Capital Level, Actual Capital Levels Ratio	8.40%	8.80%
Common Equity Tier 1 Capital level, Actual Capital Levels Ratio	11.30%	11.90%
Total Risk-Based Capital Level, Actual Capital Levels Ratio	12.30%	12.90%
Tier 1 Risk-Based Capital Level, Actual Capital Levels Ratio	11.30%	11.90%
Leverage Capital Level, Minimum Regulatory Capital Ratios Amount	$ 63,254	$ 61,832
Common Equity Tier 1 Risk-Based Capital Level, Minimum Regulatory Capital Ratios Amount	53,407	51,696
Total Risk-Based Capital Level, Minimum Regulatory Capital Ratios Amount	94,946	91,904
Tier 1 Risk-Based Capital Level, Minimum Regulatory Capital Ratios Amount	$ 71,209	$ 68,928
Leverage Capital Level, Minimum Regulatory Capital Ratios	4.00%	4.00%
Common Equity Tier 1 Risk-Based Capital Level, Minimum Regulatory Catial Ratios	4.50%	4.50%
Total Risk-Based Capital Level, Minimum Regulatory Capital Ratios	8.00%	8.00%
Tier 1 Risk-Based Capital Level, Minimum Regulatory Capital Ratios	6.00%	6.00%
Leverage Capital Level, Minimum Required To be Considered Well-Capitalized Amount	$ 79,068	$ 77,290
Common Equity Tier 1 Risk-Based Capital Level, Minimum Required To Be Considered Well-Capitalized Amount	77,143	74,672
Total Risk-Based Capital Level, Minimum Required To be Considered Well-Capitalized Amount	118,682	114,880
Tier 1 Risk-Based Capital Level, Minimum Required To be Considered Well-Capitalized Amount	$ 94,946	$ 91,904
Leverage Capital Level, Minimum Required To be Considered Well-Capitalized Ratio	5.00%	5.00%
Common Equity Tier 1 Risk-Based Capital Level, Minimum Required To Be Considered Well-Capitalized Ratio	6.50%	6.50%
Total Risk-Based Capital Level, Minimum Required To be Considered Well-Capitalized Ratio	10.00%	10.00%
Tier 1 Risk-Based Capital Level, Minimum Required To be Considered Well-Capitalized Ratio	8.00%	8.00%
Tier 1 Capital to Average Total Assets	$ 1,600,000	$ 1,500,000
Risk-Weighted Regulatory Capital Assets	$ 1,200,000	$ 1,100,000