Regulatory Matters (Details) $ in Thousands	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Company
Total Capital (to risk-weighted assets)
Total Capital (to risk-weighted assets), Actual, Capital Amount	$ 1,558,187	$ 1,507,968
Total Capital (to risk weighted assets), Actual, Ratio (as a percent)	0.124	0.122
Total Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 1,006,425	$ 992,883
Total Capital (to risk weighted assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.080	0.080
Tier I Capital (to risk-weighted assets)
Tier I Capital, (to risk-weighted assets), Actual, Capital Amount	$ 1,495,800	$ 1,452,456
Tier I Capital (to risk weighted assets), Actual, Ratio (as a percent)	0.119	0.117
Tier I Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 754,818	$ 744,662
Tier I Capital (to risk weighted assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.060	0.060
Common Equity Tier I Capital 1 (to risk-weighted assets)
Common Equity Tier I Capital 1, Actual, Capital Amount	$ 996,192	$ 952,848
Common Equity Tier I Capital 1 (to risk weighted assets), Ratio (as a percent)	0.079	0.077
Common Equity Tier I Capital 1, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 566,114	$ 558,497
Common Equity Tier I Capital 1 (to risk weighted assets, Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.045	0.045
Tier 1 Capital (to average assets)
Tier 1 Capital, Actual, Capital Amount	$ 1,495,800	$ 1,452,456
Tier 1 Capital (to average assets), Actual, Ratio (as a percent)	0.116	0.117
Tier 1 Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 514,725	$ 497,604
Tier 1 Capital (to average assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.040	0.040
Merchants Bank
Total Capital (to risk-weighted assets)
Total Capital (to risk-weighted assets), Actual, Capital Amount	$ 1,488,469	$ 1,427,738
Total Capital (to risk weighted assets), Actual, Ratio (as a percent)	0.121	0.117
Total Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 986,980	$ 975,853
Total Capital (to risk weighted assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.080	0.080
Total capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 1,233,725	$ 1,219,817
Total Capital (to risk weighted assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.100	0.100
Tier I Capital (to risk-weighted assets)
Tier I Capital, (to risk-weighted assets), Actual, Capital Amount	$ 1,426,815	$ 1,372,941
Tier I Capital (to risk weighted assets), Actual, Ratio (as a percent)	0.116	0.113
Tier I Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 740,235	$ 731,890
Tier I Capital (to risk weighted assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.060	0.060
Tier I Capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 986,980	$ 975,853
Tier I Capital (to risk weighted assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.080	0.080
Common Equity Tier I Capital 1 (to risk-weighted assets)
Common Equity Tier I Capital 1, Actual, Capital Amount	$ 1,426,815	$ 1,372,941
Common Equity Tier I Capital 1 (to risk weighted assets), Ratio (as a percent)	0.116	0.113
Common Equity Tier I Capital 1, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 555,176	$ 548,917
Common Equity Tier I Capital 1 (to risk weighted assets, Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.045	0.045
Common Equity Tier I Capital 1, Minimum Amount To Be Well Capitalized, Capital Amount	$ 801,921	$ 792,881
Common Equity Tier I Capital 1 (to risk weighted assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.065	0.065
Tier 1 Capital (to average assets)
Tier 1 Capital, Actual, Capital Amount	$ 1,426,815	$ 1,372,941
Tier 1 Capital (to average assets), Actual, Ratio (as a percent)	0.113	0.113
Tier 1 Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 503,987	$ 487,511
Tier 1 Capital (to average assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.040	0.040
Tier 1 Capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 629,983	$ 609,389
Tier 1 Capital (to average assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.050	0.050
FMBI
Total Capital (to risk-weighted assets)
Total Capital (to risk-weighted assets), Actual, Capital Amount	$ 36,044	$ 34,769
Total Capital (to risk weighted assets), Actual, Ratio (as a percent)	0.114	0.113
Total Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 25,309	$ 24,703
Total Capital (to risk weighted assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.080	0.080
Total capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 31,636	$ 30,878
Total Capital (to risk weighted assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.100	0.100
Tier I Capital (to risk-weighted assets)
Tier I Capital, (to risk-weighted assets), Actual, Capital Amount	$ 35,311	$ 34,054
Tier I Capital (to risk weighted assets), Actual, Ratio (as a percent)	0.112	0.110
Tier I Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 18,981	$ 18,527
Tier I Capital (to risk weighted assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.060	0.060
Tier I Capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 25,309	$ 24,703
Tier I Capital (to risk weighted assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.080	0.080
Common Equity Tier I Capital 1 (to risk-weighted assets)
Common Equity Tier I Capital 1, Actual, Capital Amount	$ 35,311	$ 34,054
Common Equity Tier I Capital 1 (to risk weighted assets), Ratio (as a percent)	0.112	0.110
Common Equity Tier I Capital 1, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 14,236	$ 13,895
Common Equity Tier I Capital 1 (to risk weighted assets, Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.045	0.045
Common Equity Tier I Capital 1, Minimum Amount To Be Well Capitalized, Capital Amount	$ 20,563	$ 20,071
Common Equity Tier I Capital 1 (to risk weighted assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.065	0.065
Tier 1 Capital (to average assets)
Tier 1 Capital, Actual, Capital Amount	$ 35,311	$ 34,054
Tier 1 Capital (to average assets), Actual, Ratio (as a percent)	0.106	0.107
Tier 1 Capital, Minimum Amount Required for Adequately Capitalized, Capital Amount	$ 13,347	$ 12,702
Tier 1 Capital (to average assets), Minimum Amount Required for Adequately Capitalized, Ratio (as a percent)	0.040	0.040
Tier 1 Capital, Minimum Amount To Be Well Capitalized, Capital Amount	$ 16,684	$ 15,878
Tier 1 Capital (to average assets), Minimum Amount To Be Well Capitalized, Ratio (as a percent)	0.050	0.050