Basis of Presentation	6 Months Ended
Jun. 30, 2025
Accounting Policies [Abstract]
Basis of Presentation	Significant Accounting Policies BASIS OF PRESENTATION AND CONSOLIDATION: As used in these notes, as well as in Management's Discussion and Analysis of Financial Condition and Results of Operations, references to “we,” “our,” “us,” and “the Corporation” refer to Isabella Bank Corporation, a Michigan corporation and registered financial holding company, our wholly-owned banking subsidiary, Isabella Bank, and our other consolidated subsidiaries. References to the “Bank” refer to Isabella Bank. The accompanying unaudited interim condensed consolidated financial statements in this Quarterly Report on Form 10-Q for the three and six-month periods ended June 30, 2025 (this “Form 10-Q”) have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In our opinion, all adjustments considered necessary for a fair presentation have been included. Operating results for the three and six-month periods ended June 30, 2025 are not necessarily indicative of the results that may be expected for the year ending December 31, 2025. For further information, refer to our Annual Report on Form 10-K for the year ended December 31, 2024, as filed with the SEC on March 12, 2025 (the “2024 Annual Report on Form 10-K”). OPERATING SEGMENTS: Segment information is prepared on the same basis that our CEO, who is our Chief Operating Decision Maker (“CODM”), manages our segments, evaluates financial results, and makes key operating decisions. While the CODM monitors the revenue streams of our various products and services, operations are managed, and financial performance is evaluated on a corporate-wide basis. Operating segments are aggregated into one as operating results for all segments are similar. Accordingly, all of the banking-related operations are considered by management to be aggregated in one reportable operating segment. The segment is also distinguished by the level of information provided to the CODM, who uses such information to review performance of various components of the business, which are then aggregated if operating performance, products and services, and geographical regions are similar. The CODM will evaluate the financial performance of our business components by evaluating revenue streams, significant expenses, and budget to actual results in assessing our reportable segment and in the determination of allocating resources. Further, the CODM uses revenue streams to evaluate product pricing and significant expenses to assess performance and evaluate return on assets. Consolidated net income is used to benchmark results against our competitors. Benchmarking and monitoring of budget to actual results are used in assessment performance and in establishing compensation. Revenue from banking operations consists primarily of loan and investment interest, deposit related fees, and wealth fees. Interest expense, provision for credit losses, compensation, and occupancy and equipment costs provide the significant expenses in our banking operations. All operations are domestic. RECLASSIFICATIONS: Certain amounts reported in the interim 2024 consolidated financial statements have been reclassified to conform with the 2025 presentation. Additionally, certain amounts reported as commercial and industrial loans have been reclassified as commercial real estate loans to conform to the June 30, 2025 presentation. Our accounting policies are materially the same as those discussed in Note 1 to the Consolidated Financial Statements included in our 2024 Annual Report on Form 10-K.

BASIS OF PRESENTATION AND CONSOLIDATION: As used in these notes, as well as in Management's Discussion and Analysis of Financial Condition and Results of Operations, references to “we,” “our,” “us,” and “the Corporation” refer to Isabella Bank Corporation, a Michigan corporation and registered financial holding company, our wholly-owned banking subsidiary, Isabella Bank, and our other consolidated subsidiaries. References to the “Bank” refer to Isabella Bank.

The accompanying unaudited interim condensed consolidated financial statements in this Quarterly Report on Form 10-Q for the three and six-month periods ended June 30, 2025 (this “Form 10-Q”) have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In our opinion, all adjustments considered necessary for a fair presentation have been included. Operating results for the three and six-month periods ended June 30, 2025 are not necessarily indicative of the results that may be expected for the year ending December 31, 2025. For further information, refer to our Annual Report on Form 10-K for the year ended December 31, 2024, as filed with the SEC on March 12, 2025 (the “2024 Annual Report on Form 10-K”).

OPERATING SEGMENTS: Segment information is prepared on the same basis that our CEO, who is our Chief Operating Decision Maker (“CODM”), manages our segments, evaluates financial results, and makes key operating decisions. While the CODM monitors the revenue streams of our various products and services, operations are managed, and financial performance is evaluated on a corporate-wide basis. Operating segments are aggregated into one as operating results for all segments are similar. Accordingly, all of the banking-related operations are considered by management to be aggregated in one reportable operating segment.

The segment is also distinguished by the level of information provided to the CODM, who uses such information to review performance of various components of the business, which are then aggregated if operating performance, products and services, and geographical regions are similar. The CODM will evaluate the financial performance of our business components by evaluating revenue streams, significant expenses, and budget to actual results in assessing our reportable segment and in the determination of allocating resources. Further, the CODM uses revenue streams to evaluate product pricing and significant expenses to assess performance and evaluate return on assets.

Consolidated net income is used to benchmark results against our competitors. Benchmarking and monitoring of budget to actual results are used in assessment performance and in establishing compensation. Revenue from banking operations consists primarily of loan and investment interest, deposit related fees, and wealth fees. Interest expense, provision for credit losses, compensation, and occupancy and equipment costs provide the significant expenses in our banking operations. All operations are domestic.

RECLASSIFICATIONS: Certain amounts reported in the interim 2024 consolidated financial statements have been reclassified to conform with the 2025 presentation. Additionally, certain amounts reported as commercial and industrial loans have been reclassified as commercial real estate loans to conform to the June 30, 2025 presentation. Our accounting policies are materially the same as those discussed in Note 1 to the Consolidated Financial Statements included in our 2024 Annual Report on Form 10-K.