Note 12 - Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted average common stock—basic (in shares)	43,690,581	42,165,213	40,565,433
Effect of potentially dilutive securities:
Add options to purchase common stock (in shares)			1,300,649
Add unvested restricted stock unit (in shares)			2,158,260
Add employee stock purchase plan (in shares)			8,240
Add convertible debt (in shares)			92,299
Weighted average common stock—diluted (in shares)	43,690,581	42,165,213	44,124,881