Note 17 - Quarterly Financial Information (Unaudited) (Details Textual) - 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
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 563,404	$ 562,388	$ 497,581	$ 400,091	$ 493,047	$ 457,747	$ 396,523	$ 332,056	$ 2,023,464	$ 1,679,373	$ 1,447,743
Gross Profit, Total	$ 204,306	200,334	178,473	141,927	$ 182,928	157,680	134,224	109,954	$ 725,040	584,786	512,421
Restatement Adjustment [Member] | Accounting Standards Update 2014-09 [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total		2,873	2,632	2,457		1,908	1,648	1,571		$ 6,928	$ 3,290
Gross Profit, Total		$ 2,449	$ 2,217	$ 1,938		$ 1,449	$ 1,303	$ 1,154