Note 11 - Employee Benefit Plans (Details Textual) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Partnership's Employee Unit Purchase Plan [Member]
Employee Stock Ownership Plan (ESOP), Shares in ESOP, Total	1,000,000		1,000,000
Employee Stock Ownership Plan (ESOP), Compensation Expense	$ 0.1	$ 0.1	$ 0.1	$ 0.1
Partnership's 401(k) Plan [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	0.3	0.3	0.8	0.9
Defined Contribution Plan, Employer Discretionary Profit Sharing Contribution Amount	$ 0.2	$ 0.1	$ 0.5	$ 0.1