Note 6 - Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]

	Time-Based RSUs					Performance-Based RSUs
				Weighted-Average				Weighted-Average
				Grant Date				Grant Date
	Shares			Fair Value		Shares		Fair Value
Balance at December 31, 2019		273,200		$	35.90		297,744	$	32.65
Vested		(71,794	)		25.62		—		—
Forfeited		(1,772	)		39.50		—		—
Balance at March 31, 2020		199,634		$	39.57		297,744	$	32.65