Note 9 - Accumulated Other Comprehensive Loss - Summary of Activity in Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Balance, beginning			$ 154,510
Reclassifications from accumulated comprehensive income (loss) to net income	$ (4)	$ 105	43	$ 211
Balance, ending	165,646		165,646
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance, beginning			(2,765)
Other comprehensive income before reclassifications			82
Reclassifications from accumulated comprehensive income (loss) to net income			130
Net other comprehensive income			212
Balance, ending	(2,553)		(2,553)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Rate Swap [Member]
Balance, beginning			369
Other comprehensive income before reclassifications			294
Reclassifications from accumulated comprehensive income (loss) to net income			(87)
Net other comprehensive income			207
Balance, ending	576		576
AOCI Attributable to Parent [Member]
Balance, beginning			(2,396)
Other comprehensive income before reclassifications			376
Reclassifications from accumulated comprehensive income (loss) to net income			43
Net other comprehensive income			419
Balance, ending	$ (1,977)		$ (1,977)