Note 8 - Components of Accumulated Other Comprehensive Loss - Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income taxes	$ 1	$ 35	$ 1,000	$ 54,000
Realized gain on available-for-sale securities, net of tax, reclassified out of accumulated other comprehensive loss	(3,000)	(66,000)	(3,000)	(99,000)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Realized securities gain, net	(4,000)	(101,000)	(4,000)	(153,000)
Income taxes	(1,000)	(35,000)	(1,000)	(54,000)
Realized gain on available-for-sale securities, net of tax, reclassified out of accumulated other comprehensive loss	$ (3,000)	$ (66,000)	$ (3,000)	$ (99,000)