Note 3 - Schedule of Adoption of New Revenue Standard Impacted the Consolidated Financial Statements - Income Statement (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended																12 Months Ended
	Jan. 01, 2018	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
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Gross sales																		$ 514,997	$ 525,936	$ 491,538
Net revenue		$ 134,332		$ 104,618		$ 152,046		$ 141,097		$ 182,277		$ 112,619		$ 134,554		$ 105,006		532,093	534,456	490,644
Cost of goods sold																		335,405	304,153	286,256
Gross profit		48,316		32,725		64,792		50,855		78,926		46,943		57,559		46,875		196,688	230,303	204,388
Operating profit																		101,496	144,418	130,056
Provision for income taxes																		16,596	38,061	40,214
Income from continuing operations		1,293	[1]	26,815	[1]	40,852	[1]	24,249	[1]	40,249	[2]	17,276	[2]	25,124	[2]	21,115	[2]	93,209	103,764	87,325
Net income		$ 1,212		$ 26,729		$ 40,419		$ 24,058		$ 40,259		$ 17,296		$ 25,030		$ 19,865		$ 92,418	$ 102,450	$ 81,678
Diluted earnings per share from continuing operations																		$ 2.77	$ 3.10	$ 2.65
Accounting Standards Updated 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Gross sales	$ 51,896																	$ (19,781)
Net revenue																		(19,781)
Cost of goods sold	31,347																	(5,753)
Gross profit																		(14,028)
Operating profit																		(14,028)
Provision for income taxes	$ 4,330																	(2,928)
Income from continuing operations																		(11,100)
Net income																		$ (11,100)
Diluted earnings per share from continuing operations																		$ (0.33)
Accounting Standards Updated 2014-09 [Member] | Amount Without Adoption of ASC 606 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Gross sales																		$ 534,778
Net revenue																		551,874
Cost of goods sold																		341,158
Gross profit																		210,716
Operating profit																		115,524
Provision for income taxes																		19,524
Income from continuing operations																		104,309
Net income																		$ 103,518
Diluted earnings per share from continuing operations																		$ 3.10

[1] Income from continuing operations includes a benefit of approximately $11,400 in the third quarter of 2018 for the release of valuation allowance against state NOLs. A similar amount was recorded as an expense in the fourth quarter of 2018 as a valuation allowance against state NOLs for a change in enacted tax laws. The Company adopted ASC 606 – Revenue from Contracts with Customers on January 1, 2018 using the modified retrospective method which does not require comparative periods, reported under ASC 605, to be restated.

[2] Income from continuing operations includes expense of $117 in the fourth quarter of 2017 as a result of the change in enacted tax rates in the U.S. and the toll tax.