Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accumulated depreciation	$ 279,144	$ 274,404
Common units, issued (in shares)	41,034,763	40,830,051
Common units, outstanding (in shares)	41,034,763	40,830,051
Preferred units, issued (in shares)	35,125,202	35,125,202
Preferred units, outstanding (in shares)	35,125,202	35,125,202
General partner units, outstanding (in shares)	1,225,409	1,225,409
General partner units, interest	1.60%	1.60%

The percentage of the general partner's ownership interest.

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- Definition

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.14)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

The number of general partner units outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 5
-Subparagraph (SAB Topic 4.F)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187171-122770

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The number of limited partner units issued.

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The number of limited partner units outstanding.

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The number of preferred units issued.

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The number of preferred units outstanding.

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