Note 3 - Mortgage-backed Securities (Details Textual) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2024	Dec. 31, 2023
Structured Mortgage-backed Securities [Member]
Notional Amount of Nonderivative Instruments	$ 18.3	$ 18.9

Nominal or face amount used to calculate payments on a nonderivative instrument.

No definition available.

Name:	us-gaap_NotionalAmountOfNonderivativeInstruments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration