Note 11 - Earnings Per Share - Securities Not Included in Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Anti-dilutive securities (in shares)	14,635,514	14,909,816	15,222,148
Share-based Payment Arrangement, Option [Member]
Anti-dilutive securities (in shares)	1,032,485	1,208,643	1,456,610
Restricted Stock Units (RSUs) [Member]
Anti-dilutive securities (in shares)	2,772,991	2,871,135	2,935,500
Convertible Debt Securities [Member]
Anti-dilutive securities (in shares)	10,830,038	10,830,038	10,830,038