Note 14 - Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance	$ 1,338,926	$ 1,396,974	$ 1,326,419
Change, net of tax	(1,971)	(600)	(5,732)
Balance	1,479,844	1,338,926	1,396,974
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance	(1,159)	(1,409)	(2,552)
Change, net of tax	2,613	250	1,143
Balance	1,454	(1,159)	(1,409)
Balance, tax	631	625	619
Change, tax	(4)	6	6
Balance, tax	627	631	625
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Balance
Change, net of tax	(5,260)
Balance	(5,260)
Balance, tax
Change, tax
Balance, tax
Accumulated Defined Benefit Plans Adjustment, Net Transition Attributable to Parent [Member]
Balance	(31,472)	(30,622)	(23,747)
Change, net of tax	676	(850)	(6,875)
Balance	(30,796)	(31,472)	(30,622)
Balance, tax	10,630	10,417	5,764
Change, tax	(510)	213	4,653
Balance, tax	10,120	10,630	10,417
AOCI Attributable to Parent [Member]
Balance	(32,631)	(32,031)	(26,299)
Change, net of tax	(1,971)	(600)	(5,732)
Balance	(34,602)	(32,631)	(32,031)
Balance, tax	11,261	11,042	6,383
Change, tax	(514)	219	4,659
Balance, tax	$ 10,747	$ 11,261	$ 11,042