Note 6 - Fair Value Measurements - Change in Fair Value Measurement Impacts Net Income (Details) - Valuation, Market Approach [Member]		Mar. 31, 2021		Dec. 31, 2020
Pull-through Rate [Member] | Interest Rate Contract [Member]
Derivative asset (liability)			[1]		[2]
Pull-through Rate [Member] | Forward Contract [Member]
Derivative asset (liability)			[1]		[2]
Current Reference Price [Member] | Interest Rate Contract [Member]
Derivative asset (liability)	[3]
Current Reference Price [Member] | Interest Rate Contract [Member] | Minimum [Member]
Derivative asset (liability)				1.0191
Current Reference Price [Member] | Interest Rate Contract [Member] | Maximum [Member]
Derivative asset (liability)				1.0302
Current Reference Price [Member] | Forward Contract [Member] | Minimum [Member]
Derivative asset (liability)		0.9851		1.0191
Current Reference Price [Member] | Forward Contract [Member] | Maximum [Member]
Derivative asset (liability)		1.0157		1.0319
Current Reference Price [Member] | Forward Contract [Member] | Weighted Average [Member]
Derivative asset (liability)		0.9930

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

[2] All contracts are valued using the same pull-through rate.

[3] Interest rate loan contracts at March 31, 2021 included a single loan.