Minimum Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Common Equity Tier 1 Capital [Abstract]
Common Equity Tier One Capital	$ 160,871	$ 162,532
CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssets	12.07%	12.97%
CommonEquityTierOneRiskBasedCapitalRequiredForCapitalAdequacy	$ 93,297	$ 87,675
CommonEquityTierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	7.00%	7.00%
Tier 1 capital to risk weighted assets
Actual Amount	$ 160,871	$ 162,532
Actual Ratio	0.1207	0.1297
Minimum Capital Requirement Amount	$ 113,289	$ 106,462
Minimum Capital Requirement Ratio	0.0850	0.0850
Total capital to risk weighted assets
Actual Amount	$ 199,132	$ 172,276
Actual Ratio	0.1494	0.1375
Minimum Capital Requirement Amount	$ 139,945	$ 131,512
Minimum Capital Requirement Ratio	0.1050	0.1050
Tier 1 capital to average assets
Actual Amount	$ 160,871	$ 162,532
Actual Ratio	0.0797	0.0837
Minimum Capital Requirement Amount	$ 80,733	$ 77,671
Minimum Capital Requirement Ratio	0.0400	0.0400
Isabella Bank [Member]
Common Equity Tier 1 Capital [Abstract]
Common Equity Tier One Capital	$ 171,255	$ 153,102
CommonEquityTierOneRiskBasedCapitalToRiskWeightedAssets	12.91%	12.28%
CommonEquityTierOneRiskBasedCapitalRequiredForCapitalAdequacy	$ 92,849	$ 87,273
CommonEquityTierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	7.00%	7.00%
CommonEquityTierOneRiskBasedCapitalRequiredToBeWellCapitalized	$ 86,217	$ 81,039
CommonEquityTierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets	6.50%	6.50%
Tier 1 capital to risk weighted assets
Actual Amount	$ 171,255	$ 153,102
Actual Ratio	0.1291	0.1228
Minimum Capital Requirement Amount	$ 112,746	$ 105,975
Minimum Capital Requirement Ratio	0.0850	0.0850
Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 106,114	$ 99,741
Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	0.0800	0.0800
Total capital to risk weighted assets
Actual Amount	$ 180,358	$ 162,846
Actual Ratio	0.1360	0.1306
Minimum Capital Requirement Amount	$ 139,274	$ 130,910
Minimum Capital Requirement Ratio	0.1050	0.1050
Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 132,642	$ 124,676
Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	0.1000	0.1000
Tier 1 capital to average assets
Actual Amount	$ 171,255	$ 153,102
Actual Ratio	0.0854	0.0797
Minimum Capital Requirement Amount	$ 80,171	$ 76,814
Minimum Capital Requirement Ratio	0.0400	0.0400
Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions Amount	$ 100,214	$ 96,018
Minimum To Be Well Capitalized Under Prompt Corrective Action Provisions Ratio	0.0500	0.0500

Common Equity Tier 1 Capital [Abstract]

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Amount of total capital as defined by regulatory framework.

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Amount of minimum total risk-based capital required for capital adequacy as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 505
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