Note 1 - Summary of Significant Accounting Policies (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2017
Number Of Wholly Owned Trusts	1	1
Retained Earnings [Member]
Reclassification of Accumulated Other Comprehensive Income Due to Tax Rate Change	$ 52
Retained Earnings [Member] | Accounting Standards Update 2018-02 [Member]
Reclassification of Accumulated Other Comprehensive Income Due to Tax Rate Change	52
AOCI Attributable to Parent [Member]
Reclassification of Accumulated Other Comprehensive Income Due to Tax Rate Change	(52)
AOCI Attributable to Parent [Member] | Accounting Standards Update 2018-02 [Member]
Reclassification of Accumulated Other Comprehensive Income Due to Tax Rate Change	$ (52)