Note 11 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year Ended December 31,
	2019	2018	2017
Option valuation assumptions:
Expected dividend yield	N/A	—%	—%
Expected volatility	N/A	50%	66%
Risk-free interest rate	N/A	2.71%	1.80%
Expected term (in years)	N/A	6.3	6.2

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contract Term (years)		Aggregate Intrinsic Value (in thousands)
Options outstanding as of December 31, 2018		1,515,461		$	9.11		6.57	$	22,125
Granted		—		$	—
Exercised		(70,288	)	$	9.74
Canceled or forfeited		(62,187	)	$	8.65
Options outstanding as of December 31, 2019		1,382,986		$	9.10		5.45	$	4,793
Exercisable as of December 31, 2019		1,192,671		$	8.46		5.19	$	4,527

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value [Table Text Block]

	Year Ended December 31,
	2019		2018		2017
Weighted average grant date fair value		N/A	$	12.63	$	5.31

Nonvested Restricted Stock Shares Activity [Table Text Block]

	Shares Outstanding			Grant Date Fair Value (per share)
Outstanding as of December 31, 2018		287,479		$	29.26
Granted		709,205		$	19.37
Vested		(231,543	)	$	17.19
Canceled or forfeited		(52,645	)	$	24.78
Outstanding as of December 31, 2019		712,496		$	23.66