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Note 11 - Pension Plan and Other Postretirement Benefits - Amounts Recognized in Consolidated Balance Sheets (Details) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Pension Plan [Member] |  |  |
Regulatory Assets: |  |  |
Unrecognized Prior Service Cost | $ 0 | $ 5 |
Unrecognized Actuarial Loss | 120,592 | 104,891 |
Total Regulatory Assets | 120,592 | 104,896 |
Projected Benefit Obligation Liability – Net Amount Recognized | (384,785) | (328,442) | $ (352,718)
Unrecognized Prior Service Credit | 0 | 5 |
Accumulated Other Comprehensive Loss: |  |  |
Unrecognized Prior Service Cost | 0 | 9 |
Unrecognized Actuarial (Gain) Loss | (82) | 137 |
Total Accumulated Other Comprehensive Loss | (82) | 146 |
Noncurrent Liability | 55,004 | 58,659 |
Unrecognized Prior Service Cost | 0 | 9 |
Executive Survivor and Supplemental Retirement Plan [Member] |  |  |
Regulatory Assets: |  |  |
Unrecognized Prior Service Cost | 0 | 20 |
Unrecognized Actuarial Loss | 2,170 | 1,768 |
Total Regulatory Assets | 2,170 | 1,788 |
Projected Benefit Obligation Liability – Net Amount Recognized | (43,966) | (39,699) | (42,308)
Unrecognized Prior Service Credit | 0 | 20 |
Accumulated Other Comprehensive Loss: |  |  |
Unrecognized Prior Service Cost | 1 | 64 |
Unrecognized Actuarial (Gain) Loss | 9,170 | 6,455 |
Total Accumulated Other Comprehensive Loss | 9,171 | 6,519 |
Unrecognized Prior Service Cost | 1 | 64 |
Other Postretirement Benefits Plan [Member] |  |  |
Regulatory Assets: |  |  |
Unrecognized Prior Service Cost | (20,363) | 0 |
Total Regulatory Assets | 14,959 | 18,094 |
Projected Benefit Obligation Liability – Net Amount Recognized | (71,437) | (71,561) | $ (69,774)
Unrecognized Prior Service Credit | (20,363) | 0 |
Unrecognized Net Actuarial Loss (Gain) | 35,322 | 18,094 |
Accumulated Other Comprehensive Loss: |  |  |
Unrecognized Prior Service Cost | (501) | 0 |
Unrecognized Actuarial (Gain) Loss | 184 | (107) |
Total Accumulated Other Comprehensive Loss | (317) | (107) |
Unrecognized Prior Service Cost | $ (501) | $ 0 |

X
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- Definition Represents unrecognized actuarial net gains (losses) pertaining to regulatory assets under a defined benefit plan. + References No definition available. + Details
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- Definition Represents the net prior service cost (credit) related to regulatory assets under a defined benefit plan. + References No definition available. + Details
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- Definition Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i-k) -URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669686-108580 + Details
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- Definition Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit. + 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 (j) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669686-108580 + Details
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- Definition Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669686-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + 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 (a) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent. + 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 (c) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109237824&loc=d3e1703-114919 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109237824&loc=d3e1731-114919 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(24)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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