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RETIREMENT PLANS: (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Retirement Benefits [Abstract] |  |  |
Service cost - benefits earned | $ 1,388 | $ 1,432 | $ 1,882
Interest cost on projected benefit obligation | 3,194 | 3,621 | 3,729
Expected return on plan assets | (3,962) | (3,940) | (3,429)
Net amortization and deferral | 1,448 | 1,205 | 1,936
Net periodic pension cost | 2,068 | 2,318 | 4,118
Net loss (gain) during the period | (1,192) | 5,366 | (6,150)
Amortization of prior service cost | 1 | 1 | 1
Amortization of unrecognized gain (loss) | (1,447) | (1,204) | (1,935)
Total recognized in other comprehensive (income) loss | 2,640 | (4,161) | 8,086
Total recognized net periodic pension cost and other comprehensive income | $ (572) | $ 6,479 | $ (3,968)

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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 + Details
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