Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accumulated depreciation	$ 204,101	$ 197,561
Common units, issued (in shares)	41,550,681	41,214,856
Common units, outstanding (in shares)	41,550,681	41,214,856
Preferred units, issued (in shares)	34,406,683	35,125,202
Preferred units, outstanding (in shares)	34,406,683	35,125,202
General partner units, interest	1.60%	1.60%
General partner units, outstanding (in shares)	1,225,409	1,225,409