Note 7 - Fair Value Accounting - Carrying Values and Fair Values of Financial Instruments (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Reported Value Measurement [Member]
2017 Notes (Level 3)	$ 90,943	$ 90,115
Estimate of Fair Value Measurement [Member]
2017 Notes (Level 3)	$ 12,075	$ 11,365