Note 8 - Debt, Credit Facility and Leases - Debt Summary (Details) - Senior Notes [Member] - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Principal	$ 512,862	$ 512,886
Unamortized discount/premium and issuance costs	(5,150)	(5,644)
Long-term debt balance	507,712	507,242
The 2028 Senior Notes [Member]
Principal	475,000	475,000
Unamortized discount/premium and issuance costs	(5,779)	(6,462)
Long-term debt balance	469,221	468,538
IQ Notes [Member]
Principal	37,862	37,886
Unamortized discount/premium and issuance costs	629	818
Long-term debt balance	$ 38,491	$ 38,704