Note 10 - Accounts Payable and Accrued Expenses - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Trade payables	$ 64,289	$ 48,309
Salaries and other payroll costs	19,888	17,977
Customer advances	1,177	576
Accrued interest	4,462	3,524
Income tax payable	43,682	8,824
Property tax payable	1,860	1,884
Scheduling and transmission	531	964
Royalty accrual	2,909	1,639
Other	14,998	7,953
Total	$ 153,796	$ 91,650