Note 6 - Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

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, 2018		284,493		$	35.79		265,659		$	32.90
Granted		108,925			36.37		124,586			36.37
Vested		(92,868	)		35.12		(92,501	)		38.36
Forfeited		(17,002	)		38.42		—			—
Balance at September 30, 2019		283,548		$	36.08		297,744		$	32.65