Note 7 - Long-term Obligations - Summary of Long-term Obligations (Details) (Parentheticals)	Sep. 30, 2018	May 01, 2018	Dec. 31, 2017
6.25% Convertible Notes Due 2018 [Member]
Interest rate on convertible notes	6.25%	6.25%	6.25%

Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant