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Parent Company Only Financial Information (Interim Condensed Statements of Cash Flows) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Operating activities |  |  |
Net Income (Loss) Attributable to Parent | $ 18,167 | $ 22,238 | $ 19,499
Adjustments to reconcile net income to cash provided by operations |  |  |
Amortization of Debt Issuance Costs | 90 | 87 | 52
Depreciation | 1,978 | 2,071 | 2,314
Deferred Income Tax Expense (Benefit) | 1,008 | 13 | (523)
Changes in operating assets and liabilities which used cash |  |  |
Other assets | (809) | (2,813) | 1,208
Accrued interest and other liabilities | 1,006 | 2,182 | 146
Net cash provided by (used in) operating activities | 23,715 | 26,937 | 25,501
Investing activities |  |  |
Payments to Acquire Equity Method Investments | (102) | (250) | 0
Purchases of equipment and premises | (4,064) | (3,205) | (1,593)
Net cash provided by (used in) investing activities | (25,779) | (106,255) | (229,635)
Financing activities |  |  |
Proceeds from Issuance of Subordinated Long-term Debt | 0 | 0 | 29,106
Cash dividends paid on common stock | (8,216) | (8,082) | (8,367)
Proceeds from the issuance of common stock | 1,617 | 1,762 | 1,593
Common stock repurchased | (3,415) | (1,124) | (13,758)
Common stock purchased for deferred compensation obligations | (1,624) | (1,189) | (1,187)
Net cash provided by (used in) financing activities | (3,188) | 12,912 | 62,824
Increase (decrease) in cash and cash equivalents | (5,252) | (66,406) | (141,310)
Cash and cash equivalents at beginning of period | 38,924 | 105,330 | 246,640
Cash and cash equivalents at end of period | 33,672 | 38,924 | 105,330
Isabella Bank Corporation and Related Companies Deferred Compensation Plan for Directors |  |  |
Adjustments to reconcile net income to cash provided by operations |  |  |
Share-based payment awards | 529 | 463 | 433
Isabella Bank Corporation Restricted Stock Plan |  |  |
Adjustments to reconcile net income to cash provided by operations |  |  |
Share-based payment awards | 253 | 147 | 86
Parent Company [Member] |  |  |
Operating activities |  |  |
Net Income (Loss) Attributable to Parent | 18,167 | 22,238 | 19,499
Adjustments to reconcile net income to cash provided by operations |  |  |
Undistributed earnings of subsidiaries | 9,335 | (18,782) | (18,139)
Amortization of Debt Issuance Costs | 90 | 87 | 52
Depreciation | 52 | 50 | 50
Deferred Income Tax Expense (Benefit) | 228 | (133) | (267)
Changes in operating assets and liabilities which used cash |  |  |
Other assets | (255) | 1,383 | (304)
Accrued interest and other liabilities | (199) | 160 | 70
Net cash provided by (used in) operating activities | 28,200 | 5,613 | 1,480
Investing activities |  |  |
Payments to Acquire Equity Method Investments | 0 | (250) | 0
Purchases of equipment and premises | (77) | 260 | (2)
Net cash provided by (used in) investing activities | (77) | 10 | (2)
Financing activities |  |  |
Proceeds from Issuance of Subordinated Long-term Debt | 0 | 0 | 29,106
Cash dividends paid on common stock | (8,216) | (8,082) | (8,367)
Proceeds from the issuance of common stock | 1,617 | 1,762 | 1,593
Common stock repurchased | (3,415) | (1,124) | (13,758)
Common stock purchased for deferred compensation obligations | (1,624) | (1,189) | (1,187)
Net cash provided by (used in) financing activities | (11,638) | (8,633) | 7,387
Increase (decrease) in cash and cash equivalents | 16,485 | (3,010) | 8,865
Cash and cash equivalents at beginning of period | 8,525 | 11,535 | 2,670
Cash and cash equivalents at end of period | 25,010 | 8,525 | 11,535
Parent Company [Member] | Isabella Bank Corporation and Related Companies Deferred Compensation Plan for Directors |  |  |
Adjustments to reconcile net income to cash provided by operations |  |  |
Share-based payment awards | 529 | 463 | 433
Parent Company [Member] | Isabella Bank Corporation Restricted Stock Plan |  |  |
Adjustments to reconcile net income to cash provided by operations |  |  |
Share-based payment awards | $ 253 | $ 147 | $ 86

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