Regulatory Matters (Details) $ in Thousands	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Company
Tier 1 Capital (to average assets)
Tier 1 Capital, Actual, Capital Amount	$ 1,217,718	$ 1,138,090
Tier 1 Capital (to average assets), Actual, Ratio (as a percent)	0.124	0.104
Tier 1 Capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 882,179	$ 928,731
Company | Minimum
Tier 1 Capital (to average assets)
Tier 1 Capital (to average assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.09	0.085
Merchants Bank
Tier 1 Capital (to average assets)
Tier 1 Capital, Actual, Capital Amount	$ 1,171,291	$ 1,088,621
Tier 1 Capital (to average assets), Actual, Ratio (as a percent)	0.123	0.103
Tier 1 Capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 857,175	$ 901,188
Merchants Bank | Minimum
Tier 1 Capital (to average assets)
Tier 1 Capital (to average assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.09	0.085
FMBI
Tier 1 Capital (to average assets)
Tier 1 Capital, Actual, Capital Amount	$ 31,104	$ 28,958
Tier 1 Capital (to average assets), Actual, Ratio (as a percent)	0.103	0.097
Tier 1 Capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 27,088	$ 25,499
FMBI | Minimum
Tier 1 Capital (to average assets)
Tier 1 Capital (to average assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.09	0.085