Note 8 - Employee Benefit Plans - Components of Net Periodic Benefit Cost to be Recognized Over Next Fiscal Year (Details) - Amounts Expected to be Recognized in 2017 [Member] $ in Thousands	Dec. 31, 2017 USD ($)
Amortization of net loss	$ 3,726
Amortization of prior service benefit	$ 61

Amount included in accumulated other comprehensive (income) loss for prior service cost (credit) expected to be recognized in net periodic benefit cost (credit) for fiscal year following most recent annual statement of financial position.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (s)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanExpectedAmortizationOfPriorServiceCostCreditNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant