Note 9 - Stock-based Compensation - Schedule of Target Multipliers (Details) - Performance Stock Unit [Member]	9 Months Ended
	Sep. 30, 2020
TSR Range Two [Member]
Company's Annualized TSR	1.00%
TSR Range Three [Member]
Company's Annualized TSR	0.50%
Minimum [Member] | TSR Range One [Member]
Company's Annualized TSR	2.00%
Maximum [Member] | TSR Range Four [Member]
Company's Annualized TSR	0.00%