Note 15 - Net Income Per Share and Common Stock Dividends (Details Textual) - Stock Appreciation Rights (SARs) [Member] shares in Thousands	12 Months Ended
Dec. 31, 2018 $ / shares shares
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount \| shares	146
Minimum [Member]
Share Price	$ 35.90
Maximum [Member]
Share Price	$ 40

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration