Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accumulated depreciation (USD)	$ 206,495	$ 204,101
Common units, issued (in shares)	41,856,847	41,550,681
Common units, outstanding (in shares)	41,856,847	41,550,681
Preferred units, issued (in shares)	34,406,683	34,406,683
Preferred units, outstanding (in shares)	34,406,683	34,406,683
General partner Ownership	1.60%	1.60%
General partner units, outstanding (in shares)	1,225,409	1,225,409