Note 13 - Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Total income tax provision		$ (4,489)	$ (6,775)	$ (7,439)	$ (12,029)
Net of tax		13,923	12,725	25,335	24,985
Total before tax		18,412	19,500	32,774	37,014
Other expense		(3,749)	(3,185)	(8,440)	(8,158)
Total before tax		18,412	19,500	32,774	37,014
Total income tax provision		4,489	6,775	7,439	12,029
Net income		13,923	12,725	25,335	24,985
Reclassification out of Accumulated Other Comprehensive Income [Member]
Total income tax provision		(40)		(78)
Net of tax		(84)		(168)
Total before tax		(124)		(246)
Total before tax		(124)		(246)
Total income tax provision		40		78
Net income		(84)		(168)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Other expense	[1]	(133)	(151)	(265)	(302)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Other expense	[1]	9	11	19	22
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Total income tax provision			59		119
Net of tax			(81)		(161)
Total before tax		(187)	(140)	(241)	(280)
Total before tax		(187)	(140)	(241)	(280)
Total income tax provision			(59)		(119)
Net income			$ (81)		$ (161)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swap [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Total income tax provision		(273)		(351)
Net of tax		86		110
Total income tax provision		273		351
Net income		$ 86		$ 110

[1] These accumulated other comprehensive income components are included in the computation of net periodic pension cost (See Note 8 of the Notes to Consolidated Financial Statements "Pension and Other Postretirement Benefit Plans".)