Note 5 - Long-term Debt (Details Textual) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Payments of Debt Issuance Costs	$ 8,757	$ 1,418
Other Line Of Credit [Member]
Long-term Line of Credit, Total	0
Line of Credit Facility, Maximum Borrowing Capacity	$ 9,600
Other Line Of Credit [Member] | Minimum [Member]
Line of Credit Facility, Interest Rate During Period	2.50%
Other Line Of Credit [Member] | Maximum [Member]
Line of Credit Facility, Interest Rate During Period	6.50%
Syndicated Facility Agreement [Member]
Letters of Credit Outstanding, Amount	$ 3,600
Long-term Debt, Weighted Average Interest Rate, at Point in Time	3.70%
Syndicated Facility Agreement [Member] | Revolving Credit Facility [Member]
Long-term Line of Credit, Total	$ 32,100
Syndicated Facility Agreement [Member] | Term Loan [Member]
Payments of Debt Issuance Costs	8,800
Long-term Debt, Total	$ 625,200