Note 4 - Derivative Instruments and Hedging Activities (Details Textual) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2020	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2017	Dec. 31, 2020 USD ($)
Derivative, Number of Instruments Held, Total		0		0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax, Total		$ 2,941	$ 1,003	$ 15,184	$ (18,406)
Derivative Assets (Liabilities), Net Fair Value of Derivative Contracts, Excluding Impact of Credit Risk		$ (9,383)		$ (9,383)			$ (28,667)
Interest Rate Swap [Member]
Number of New Contracts Entered	3					20
Derivative, Number of Instruments Outstanding		15		15
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax, Total		$ 2,941	$ 1,003	$ 15,184	$ (18,406)