Note 9 - Senior Notes and Unsecured Revolving Credit Facility - Indebtedness (Details) (Parentheticals)	Dec. 31, 2019	Dec. 31, 2018	Mar. 17, 2017
Senior Notes [Member] \| Senior Notes Due 2022 [Member]
Debt Instrument, Interest Rate, Stated Percentage	7.25%	7.25%	7.25%

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