Defined benefit plan effect on pension expense.

No definition available.

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- Definition

Unrecognized Actuarial Gain (Loss) in Excess of Benefit Obligation, Percentage.

+ References

No definition available.

+ Details

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- Definition

Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate.

+ 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 (m)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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- Definition

Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate.

+ References

+ Details

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- Definition

Amount of increase in accumulated postretirement benefit obligation from one-percentage-point increase in assumed health care cost trend rate.

+ References

+ Details

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- Definition

Amount of increase in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point increase in assumed health care cost trend rate.

+ References

+ Details

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- Definition

Amount of contributions expected to be received by defined benefit plan from employer in fiscal year. Excludes contributions paid by employer in current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2709-114920

+ Details

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ 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 (d)(5)(i)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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Period Type:	instant

- Definition

Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

+ 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 (h)(7)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ 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 (l)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

+ Details

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Period Type:	instant

- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

+ References

No definition available.

+ Details

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- Details

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Note 7 - Pensions and Other Postretirement Benefits (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ 4,000,000	$ 0	$ 3,800,000
Unrecognized Actuarial Gain (Loss) in Excess of Benefit Obligation, Percentage	10.00%
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	$ 271,000
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	1,600,000
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components	233,000
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	$ 1,400,000
Minimum [Member] \| Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	7.00%
Minimum [Member] \| Fixed Income Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	70.00%
Minimum [Member] \| Alternative Investments [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Minimum [Member] \| Cash and Cash Equivalents [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Maximum [Member] \| Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	27.00%
Maximum [Member] \| Fixed Income Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	90.00%
Maximum [Member] \| Alternative Investments [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	6.00%
Maximum [Member] \| Cash and Cash Equivalents [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%
One Percentage Point Change in Assumed Rate of Return [Member]
Defined Benefit Plan Effect On Pension Expense	$ 783,000
One Percentage Point Increase in Discount Rate [Member]
Defined Benefit Plan Effect On Pension Expense	1,200,000
One Percentage Point Decrease in Discount Rate [Member]
Defined Benefit Plan Effect On Pension Expense	1,400,000
Pension Plan [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	1,900,000	$ 1,600,000	$ 1,600,000
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 2,000,000
Postretirement Health Coverage [Member] \| Retirees Age65 And Over [Member]
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	0.00%
Postretirement Health Coverage [Member] \| Retirees Under Age65 [Member]
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%