Note 2 - Earnings Per Share - Securities that Potentially Dilute Calculation of Diluted Earnings Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Antidilutive securities (in shares)	1,244,557	2,169,426
Stock Appreciation Rights (SARs) [Member]
Antidilutive securities (in shares)	68,638
Employee Stock Option [Member]
Antidilutive securities (in shares)	358	3,846
Restricted Stock [Member]
Antidilutive securities (in shares)	16	268
Convertible 2017 Notes [Member]
Antidilutive securities (in shares)	1,116,637	1,485,100
Convertible 2020 Notes [Member]
Antidilutive securities (in shares)		21
Warrant [Member]
Antidilutive securities (in shares)	58,902	680,119
Warrants Classified as Equity [Member]
Antidilutive securities (in shares)	6	72