v3.26.3
Note 14 - Regulatory Matters - Actual Capital Levels and Minimum Levels (Details)
$ in Thousands
Sep. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Total capital minimum required for capital adequacy, ratio 0.105  
Tier 1 capital minimum required for capital adequacy, ratio 0.085  
Common equity tier 1 capital minimum required for capital adequacy, ratio 0.07  
Consolidated Entities [Member]    
Total capital, amount $ 917,167 $ 859,158
Total capital, ratio 0.146 0.144
Total capital minimum required for capital adequacy, amount $ 502,714 $ 477,044
Total capital minimum required for capital adequacy, ratio 0.08 0.08
Tier 1 capital, amount $ 768,377 $ 709,058
Tier 1 capital, ratio 0.122 0.119
Tier 1 capital minimum required for capital adequacy, amount $ 377,035 $ 357,783
Tier 1 capital minimum required for capital adequacy, ratio 0.06 0.06
Common equity tier 1, amount $ 718,922 $ 660,117
Common equity tier 1, ratio 0.114 0.111
Common equity tier 1 minimum required for capital adequacy, amount $ 282,777 $ 268,337
Common equity tier 1 capital minimum required for capital adequacy, ratio 0.045 0.045
Tier 1 capital to average assets, amount $ 768,377 $ 709,058
Tier 1 capital to average assets, ratio 0.111 0.114
Tier 1 capital to average assets, minimum required for capital adequacy, amount $ 276,647 $ 249,580
Tier 1 capital to average assets minimum required for capital adequacy, ratio 0.04 0.04
Mercantile Bank [Member]    
Total capital, amount $ 791,783 $ 775,664
Total capital, ratio 0.134 0.138
Total capital minimum required for capital adequacy, amount $ 473,476 $ 449,498
Total capital minimum required for capital adequacy, ratio 0.08 0.08
Total capital to be well capitalized, amount $ 591,845 $ 561,873
Total capital to be well capitalized, ratio 0.10 0.10
Tier 1 capital, amount $ 735,149 $ 717,619
Tier 1 capital, ratio 0.124 0.128
Tier 1 capital minimum required for capital adequacy, amount $ 355,107 $ 337,124
Tier 1 capital minimum required for capital adequacy, ratio 0.06 0.06
Tier 1 capital to be well capitalized, amount $ 473,476 $ 449,498
Tier 1 capital to be well capitalized, ratio 0.08 0.08
Common equity tier 1, amount $ 735,149 $ 717,619
Common equity tier 1, ratio 0.124 0.128
Common equity tier 1 minimum required for capital adequacy, amount $ 266,330 $ 252,843
Common equity tier 1 capital minimum required for capital adequacy, ratio 0.045 0.045
Common equity tier 1 capital to be well capitalized, amount $ 384,699 $ 365,217
Common equity tier 1 capital to be well capitalized, ratio 0.065 0.065
Tier 1 capital to average assets, amount $ 735,149 $ 717,619
Tier 1 capital to average assets, ratio 0.116 0.115
Tier 1 capital to average assets, minimum required for capital adequacy, amount $ 254,361 $ 248,738
Tier 1 capital to average assets minimum required for capital adequacy, ratio 0.04 0.04
Tier 1 capital to average assets to be well capitalized, amount $ 317,952 $ 310,922
Tier 1 capital to average assets to be well capitalized, ratio 0.05 0.05
Eastern Michigan Bank [Member]    
Total capital, amount $ 66,569 $ 58,893
Total capital, ratio 0.239 0.202
Total capital minimum required for capital adequacy, amount $ 22,293 $ 23,335
Total capital minimum required for capital adequacy, ratio 0.08 0.08
Total capital to be well capitalized, amount $ 27,866 $ 29,168
Total capital to be well capitalized, ratio 0.10 0.10
Tier 1 capital, amount $ 64,326 $ 56,495
Tier 1 capital, ratio 0.231 0.194
Tier 1 capital minimum required for capital adequacy, amount $ 16,720 $ 17,501
Tier 1 capital minimum required for capital adequacy, ratio 0.06 0.06
Tier 1 capital to be well capitalized, amount $ 22,293 $ 23,335
Tier 1 capital to be well capitalized, ratio 0.08 0.08
Common equity tier 1, amount $ 64,326 $ 56,495
Common equity tier 1, ratio 0.231 0.194
Common equity tier 1 minimum required for capital adequacy, amount $ 12,540 $ 13,126
Common equity tier 1 capital minimum required for capital adequacy, ratio 0.045 0.045
Common equity tier 1 capital to be well capitalized, amount $ 18,113 $ 18,960
Common equity tier 1 capital to be well capitalized, ratio 0.065 0.065
Tier 1 capital to average assets, amount $ 64,326 $ 56,495
Tier 1 capital to average assets, ratio 0.12 0.115
Tier 1 capital to average assets, minimum required for capital adequacy, amount $ 21,511 $ 19,621
Tier 1 capital to average assets minimum required for capital adequacy, ratio 0.04 0.04
Tier 1 capital to average assets to be well capitalized, amount $ 26,889 $ 24,527
Tier 1 capital to average assets to be well capitalized, ratio 0.05 0.05