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RETIREMENT PLANS: (Details 4) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items] |  |
Schedule of Allocation of Plan Assets [Table Text Block] | The Corporation's pension plan weighted-average asset allocation for the years 2018 and 2017 by asset category are as follows:
|  | Pension Plan Target Allocation |  | ESOP Target Allocation |  | Pension Percentage of Plan Assets at December 31, |  | ESOP Percentage of Plan Assets at December 31,
ASSET CATEGORY |  | 2018 |  | 2018 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Equity securities |  | 25-75% |  | 95-99% |  | 65 | % |  | 72 | % |  | 99 | % |  | 98 | %
Debt securities |  | 0-50% |  | 0-0% |  | 31 | % |  | 25 | % |  | — | % |  | — | %
Other |  | 0-20% |  | 0-5% |  | 4 | % |  | 3 | % |  | 1 | % |  | 2 | %
TOTAL |  |  |  |  |  | 100 | % |  | 100 | % |  | 100 | % |  | 100 | %
Percentage of plan assets (percent) | 100.00% | 100.00%
Employee Stock Ownership Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets (percent) | 100.00% | 100.00%
Other Securities [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets (percent) | 4.00% | 3.00%
Other Securities [Member] | Employee Stock Ownership Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of plan assets (percent) | 1.00% | 2.00%
Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Schedule of Allocation of Plan Assets [Table Text Block] | 0 |
Percentage of plan assets (percent) | 65.00% | 72.00%
Equity Securities | Employee Stock Ownership Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Schedule of Allocation of Plan Assets [Table Text Block] | 0 |
Percentage of plan assets (percent) | 99.00% | 98.00%
Debt securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Schedule of Allocation of Plan Assets [Table Text Block] | 0 |
Percentage of plan assets (percent) | 31.00% | 25.00%
Debt securities | Employee Stock Ownership Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Schedule of Allocation of Plan Assets [Table Text Block] | 0 |
Percentage of plan assets (percent) | 0.00% | 0.00%
Other Security Investments [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Schedule of Allocation of Plan Assets [Table Text Block] | 0 |
Other Security Investments [Member] | Employee Stock Ownership Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Schedule of Allocation of Plan Assets [Table Text Block] | 0 |

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- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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