Note 16 - Accumulated Other Comprehensive Loss - Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Actuarial losses									$ (747)	$ (1,340)	$ (1,800)
Selling, general and administrative expenses									68,506	68,984	58,042
Income before income taxes									109,805	141,825	127,539
Tax benefit									(16,596)	(38,061)	(40,214)
Total reclassification for the period, net of tax	$ (1,212)	$ (26,729)	$ (40,419)	$ (24,058)	$ (40,259)	$ (17,296)	$ (25,030)	$ (19,865)	(92,418)	(102,450)	$ (81,678)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Actuarial losses									(1,224)	(1,400)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Selling, general and administrative expenses									5	(52)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Income before income taxes									(1,219)	(1,452)
Tax benefit									277	531
Total reclassification for the period, net of tax									$ (942)	$ (921)