Note 8 - Accumulated Other Comprehensive Loss - Summary of Activity in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Balance, beginning			$ 157,831
Total other comprehensive income	$ 140	$ 58	476	$ 255
Balance at September 30, 2017	155,217		155,217
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance, beginning			(2,875)
Other comprehensive income before reclassifications			52
Reclassifications from accumulated comprehensive loss to net income			272
Total other comprehensive income			324
Balance at September 30, 2017	(2,551)		(2,551)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Rate Swap [Member]
Balance, beginning			(35)
Other comprehensive income before reclassifications			104
Reclassifications from accumulated comprehensive loss to net income			48
Total other comprehensive income			152
Balance at September 30, 2017	117		117
AOCI Attributable to Parent [Member]
Balance, beginning			(2,910)
Other comprehensive income before reclassifications			156
Reclassifications from accumulated comprehensive loss to net income			320
Total other comprehensive income			476
Balance at September 30, 2017	$ (2,434)		$ (2,434)