Note 2 - New Accounting Pronouncements - Effect of the Initial Application of New Standard in the Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Prepaid expenses and other	$ 18,224	$ 16,056	$ 51,441
Deferred financing and lease costs, net	1,733	1,583	3,242
Property, plant and equipment, net	1,962,580	1,946,723	1,959,578
Operating leases right of use	60,656	62,244
Finance leases right of use	14,433	13,476
Accounts payable and accrued expenses	108,309	113,502	116,362
Current maturity of operating lease liabilities	7,532	7,532
Finance lease liabilities	3,147	2,841
Other long-term liabilities	5,464	6,117	16,087
Long term portion of operating lease liabilities	17,667	17,668
Long term portion of finance lease liabilities	11,954	10,668
Retained earnings	$ 442,531	422,164	$ 422,222
Accounting Standards Update 2016-02 [Member]
Prepaid expenses and other		(35,385)
Deferred financing and lease costs, net		(1,659)
Property, plant and equipment, net		(12,855)
Operating leases right of use		62,244
Finance leases right of use		13,476
Accounts payable and accrued expenses		(2,860)
Current maturity of operating lease liabilities		7,532
Finance lease liabilities		2,841
Other long-term liabilities		(9,970)
Long term portion of operating lease liabilities		17,668
Long term portion of finance lease liabilities		10,668
Retained earnings		$ (58)