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Note 9 - Share-based Compensation (Details Textual) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Number Of Active Stock Incentive Plans	1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)	24,000
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 24.15
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)	0
Restricted Stock Units and Performance Share Award Target Level, Percentage	100.00%
Performance Awards Issued Multiplier	136.00%
Minimum [Member]
Performance Awards Issued Multiplier	0.00%
Maximum [Member]
Performance Awards Issued Multiplier	200.00%
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Month)	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	10 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Month)	3 years
Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number At Target Level Of Performance (in shares)	91,000
Restricted Stock Units and Performance Stock Awards [Member]
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount | $	$ 4.2
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	2 years

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