Note 1 - Summary of Significant Accounting Policies (Details Textual) $ in Thousands		6 Months Ended
	Jan. 01, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017
Number Of Wholly Owned Trusts		1	1
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
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