Note 12 - Stock Repurchase Program (Details Textual) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended		38 Months Ended
	Oct. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Oct. 01, 2018	Aug. 31, 2015
Stock Repurchase Program, Authorized Amount	$ 250,000					$ 200,000
Stock Repurchase Program, Period in Force	2 years
Payments for Repurchase of Common Stock		$ 25,656	$ 30,012	$ 305,547
Subsequent Event [Member]
Stock Repurchase Program, Authorized Amount					$ 250,000
Treasury Stock [Member]
Shares Acquired Under Stock Repurchases Program, Shares		560,000	844,500	8,676,706