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Note 6 - Accrued Retirement Benefits (Details Textual) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2016 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2012 USD ($) a
Defined Benefit Plan, Number of Participants Offered a One-time Lump Sum Payment | 500 |  |  |  |
Defined Benefit Plan, Number of Participants Who Accepted a One-time Lump Sum Payment | 325 |  |  |  |
Defined Benefit Plan, Settlements, Benefit Obligation | $ 9,300 |  | $ 10,103 |  |
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Actuarial Gain (Loss), before Tax |  |  | 22,300 | 28,700 |
Defined Benefit Plan, Additional Security to Support Unfunded Liabilities |  |  |  |  | $ 18,700
Defined Benefit Plan, Area of Real Estate Property Pledged as Security | a |  |  |  |  | 6,800
Defined Benefit Plan, Period for Release of Real Estate Property Pledged as Security |  |  |  |  | 5 years
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year |  |  | 0 |  |
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year |  |  | $ 0 | $ 0 |
Scenario, Forecast [Member] |  |  |  |  |
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss), Net Actuarial Gain (Loss), before Tax |  | $ 800 |  |  |

X
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- Definition Represents the area of real estate property pledged as security. + References No definition available. + Details
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- Definition The number of participants who were offered a one-time lump sum payment under a defined benefit plan. + References No definition available. + Details
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- Definition The number of participants who accepted a one-time lump sum payment under a defined benefit plan. + References No definition available. + Details
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- Definition Amount before tax, after reclassification adjustments, of actuarial gain (loss) that has not been recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669646-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The amount of decrease that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 15 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Amount of employer's best estimate of contributions expected to be paid to the plan in the current remaining fiscal period. + References No definition available. + Details
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- Definition Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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