Note 12 - Accumulated Other Comprehensive (Loss)/Income - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Net of tax	$ (2,699)		$ (4,695)
Pension plan amortization of actuarial losses	(353)	$ (181)	(425)	$ (445)
Prior service (credit) costs	25,695	15,668	50,736	32,523
Income before income taxes	23,559	49,600	37,618	79,635
Tax benefit	(7,872)	(8,748)	(11,404)	(14,534)
Amounts reclassified from accumulated other comprehensive loss	15,618	40,419	26,027	64,477
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Amounts reclassified from accumulated other comprehensive loss	(269)	(206)	(516)	(501)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Interest rate swap	(30)		(36)
Net of tax	(30)		(36)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Pension plan amortization of actuarial losses	(321)	(276)	(644)	(680)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Prior service (credit) costs		(1)		(2)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Income before income taxes		(275)		(678)
Tax benefit	82	$ 69	164	$ 177
Amounts reclassified from accumulated other comprehensive loss	$ (239)		$ (480)