Note 7 - Partners' Capital and Distributions (Details Textual) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($) $ / shares
Preferred Unit, Cash Distribution [Member]
Distribution Made to Limited Partner, Declaration Date	Apr. 16, 2020
Distribution Made to Limited Partner, Distributions Declared, Per Unit (in dollars per share) \| $ / shares	$ 0.17875
Distribution Made to Limited Partner, Distribution Date	May 14, 2020
Distribution Made to Limited Partner, Date of Record	May 04, 2020
Distribution Made to Limited Partner, Cash Distributions Declared	$ 6.4
Preferred Unit, Cash Distribution [Member] \| Preferred Partner [Member]
Distribution Made to Limited Partner, Cash Distributions Declared	6.3
Preferred Unit, Cash Distribution [Member] \| General Partner [Member] \| Maximum [Member]
Distribution Made to Limited Partner, Cash Distributions Declared	$ 0.1
Common Unit, Cash Distribution [Member]
Distribution Made to Limited Partner, Declaration Date	Apr. 16, 2020
Distribution Made to Limited Partner, Distributions Declared, Per Unit (in dollars per share) \| $ / shares	$ 0.04
Distribution Made to Limited Partner, Distribution Date	May 14, 2020
Distribution Made to Limited Partner, Date of Record	May 04, 2020
Distribution Made to Limited Partner, Cash Distributions Declared	$ 1.7
Common Unit, Cash Distribution [Member] \| General Partner [Member] \| Maximum [Member]
Distribution Made to Limited Partner, Cash Distributions Declared	0.1
Common Unit, Cash Distribution [Member] \| Limited Partner [Member]
Distribution Made to Limited Partner, Cash Distributions Declared	1.6
Phantom and Restricted Units Holders [Member]
Distribution Made to Limited Partner, Cash Distributions Declared	$ 0.1

Amount of equity impact of cash distribution declared to unit-holder of limited partnership (LP).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

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