Note 7 - Fair Value Measurements - Change in Fair Value Measurement Impacts Net Income (Details) - Valuation, Market Approach [Member]		Sep. 30, 2020	Dec. 31, 2019
Pull-through Rate [Member] | Minimum [Member] | Interest Rate Contract [Member]
Derivative asset (liability)		0.8582
Derivative asset (liability)		(0.8582)
Pull-through Rate [Member] | Minimum [Member] | Forward Contract [Member]
Derivative asset (liability)		0.8582
Derivative asset (liability)		(0.8582)
Pull-through Rate [Member] | Maximum [Member] | Interest Rate Contract [Member]
Derivative asset (liability)		1.0000
Derivative asset (liability)		(1.0000)
Pull-through Rate [Member] | Maximum [Member] | Forward Contract [Member]
Derivative asset (liability)		1.0000
Derivative asset (liability)		(1.0000)
Pull-through Rate [Member] | Weighted Average [Member] | Interest Rate Contract [Member]
Derivative asset (liability)		0.9239
Derivative asset (liability)		(0.9239)
Pull-through Rate1 [Member] | Weighted Average [Member] | Forward Contract [Member]
Derivative asset (liability)		0.9239
Derivative asset (liability)		(0.9239)
Current Reference Price [Member] | Minimum [Member] | Interest Rate Contract [Member]
Derivative asset (liability)		1.0146	1.0149
Derivative asset (liability)		(1.0146)	(1.0149)
Current Reference Price [Member] | Minimum [Member] | Forward Contract [Member]
Derivative asset (liability)		1.0146
Derivative asset (liability)		(1.0146)
Current Reference Price [Member] | Minimum [Member] | Forward Contracts [Member]
Derivative asset (liability)			1.0149
Derivative asset (liability)			(1.0149)
Current Reference Price [Member] | Maximum [Member] | Interest Rate Contract [Member]
Derivative asset (liability)		1.0436	1.0206
Derivative asset (liability)		(1.0436)	(1.0206)
Current Reference Price [Member] | Maximum [Member] | Forward Contract [Member]
Derivative asset (liability)		1.0436
Derivative asset (liability)		(1.0436)
Current Reference Price [Member] | Maximum [Member] | Forward Contracts [Member]
Derivative asset (liability)			1.0328
Derivative asset (liability)			(1.0328)
Current Reference Price [Member] | Weighted Average [Member] | Interest Rate Contract [Member]
Derivative asset (liability)	[1]	1.0247	1.0172
Derivative asset (liability)	[1]	(1.0247)	(1.0172)
Current Reference Price [Member] | Weighted Average [Member] | Forward Contract [Member]
Derivative asset (liability)	[1]	1.0260
Derivative asset (liability)	[1]	(1.0260)
Current Reference Price [Member] | Weighted Average [Member] | Forward Contracts [Member]
Derivative asset (liability)	[1]		1.0191
Derivative asset (liability)	[1]		(1.0191)

[1] Current reference prices were weighted by the relative amount of the loan