Note 9 - Accumulated Other Comprehensive Loss - Activity in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income (loss), net of tax	$ 471			$ 1,489			$ 471	$ 1,489	$ (659)	$ (254)
Other comprehensive income (loss), net of tax	(41)	$ 915	$ 256	(222)	$ 519	$ 1,446	1,130	1,743	(405)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated other comprehensive income (loss), net of tax	471			1,489			$ 471	1,489	$ (659)	1,142
Other comprehensive income (loss), net of tax	$ (41)	$ 915	$ 256	(222)	519	50
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated other comprehensive income (loss), net of tax										$ (1,396)
Other comprehensive income (loss), net of tax						$ 1,396