Note 9 - Accumulated Other Comprehensive Loss - Summary of Activity in Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Balance, beginning			$ 154,510
Reclassifications from accumulated comprehensive income (loss) to net income	$ (106)	$ 109	(63)	$ 320
Balance, ending	168,038		168,038
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance, beginning			(2,765)
Other comprehensive income before reclassifications			121
Reclassifications from accumulated comprehensive income (loss) to net income			121
Net other comprehensive income			242
Balance, ending	(2,523)		(2,523)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Rate Swap [Member]
Balance, beginning			369
Other comprehensive income before reclassifications			306
Reclassifications from accumulated comprehensive income (loss) to net income			(184)
Net other comprehensive income			122
Balance, ending	491		491
AOCI Attributable to Parent [Member]
Balance, beginning			(2,396)
Other comprehensive income before reclassifications			427
Reclassifications from accumulated comprehensive income (loss) to net income			(63)
Net other comprehensive income			364
Balance, ending	$ (2,032)		$ (2,032)