Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]: Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Details
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost	$ 35,343
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value	35,734
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost	182,202
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value	186,854
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Amortized Cost	114,132
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Fair Value	114,533
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10	71,949
Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10	71,375
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	10,665
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value	10,788
Debt Securities, Available-for-sale, Amortized Cost	414,291	$ 383,425
Debt Securities, Available-for-sale	$ 419,284	$ 384,974

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amortized cost of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), without single maturity date and not allocated over maturity grouping.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Name Accounting Standards Codification
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