Note 7 - Regulatory Capital - Actual and Required Capital Amount and Ratio (Details) $ in Thousands	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Consolidated Waterstone Financial Inc [Member]
Total capital (to risk-weighted assets)	$ 374,807	$ 380,351
Total capital (to risk-weighted assets) Ratio	0.2074	0.215
Total capital (to risk-weighted assets), For Capital Adequacy Purposes	$ 144,580	$ 141,538
Total capital (to risk-weighted assets), For Capital Adequacy Ratio	0.08	0.08
Total capital (to risk-weighted assets), Minimum Capital Adequacy with Capital Buffer	$ 189,760	$ 185,769
Total capital (to risk-weighted assets), Minimum Capital Adequacy with Capital Buffer Ratio	10.50%	10.50%
Tier I capital (to risk-weighted assets)	$ 355,637	$ 360,734
Tier I capital (to risk-weighted assets) Ratio	0.1968	0.2039
Tier I capital (to risk-weighted assets), For Capital Adequacy Purposes	$ 108,440	$ 106,154
Tier I capital (to risk-weighted assets), For Capital Adequacy Ratio	0.06	0.06
Tier I capital (to risk weighted assets), Minimum Capital Adequacy with Capital Buffer	$ 153,620	$ 150,385
Tier I capital (to risk weighted assets), Minimum Capital Adequacy with Capital Buffer Ratio	8.50%	8.50%
Common Equity Tier 1 Capital (to risk-weighted assets)	$ 355,637	$ 360,734
Common Equity Tier 1 capital (to risk-weighted assets) Ratio	0.1968	0.2039
Common Equity Tier I capital (to risk weighted assets), For Capital Adequacy Purposes	$ 81,330	$ 79,615
Common Equity Tier I capital (to risk-weighted), For Capital Adequacy Ratio	0.045	0.045
Common Equity Tier I capital (to risk weighted assets) Minimum Capital Adequacy with Capital Buffer	$ 126,510	$ 123,846
Common Equity Tier I capital (to risk weighted), Minimum Capital Adequacy with Capital Buffer Ratio	7.00%	7.00%
Tier I capital (to average assets)	$ 355,637	$ 360,734
Tier I capital (to average assets) Ratio	0.1562	0.1677
Tier I capital (to average assets), For Capital Adequacy Purposes	$ 91,070	$ 86,043
Tier I capital (to average assets), For Capital Adequacy Ratio	0.04	0.04
Subsidiaries [Member]
Total capital (to risk-weighted assets)	$ 359,791	$ 355,476
Total capital (to risk-weighted assets) Ratio	0.1991	0.201
Total capital (to risk-weighted assets), For Capital Adequacy Purposes	$ 144,570	$ 141,515
Total capital (to risk-weighted assets), For Capital Adequacy Ratio	0.08	0.08
Total capital (to risk-weighted assets), Minimum Capital Adequacy with Capital Buffer	$ 189,740	$ 185,738
Total capital (to risk-weighted assets), Minimum Capital Adequacy with Capital Buffer Ratio	10.50%	10.50%
Total capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions	$ 180,709	$ 176,893
Total capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio	0.10	0.10
Tier I capital (to risk-weighted assets)	$ 340,621	$ 335,859
Tier I capital (to risk-weighted assets) Ratio	0.1885	0.1899
Tier I capital (to risk-weighted assets), For Capital Adequacy Purposes	$ 108,420	$ 106,117
Tier I capital (to risk-weighted assets), For Capital Adequacy Ratio	0.06	0.06
Tier I capital (to risk weighted assets), Minimum Capital Adequacy with Capital Buffer	$ 153,600	$ 150,332
Tier I capital (to risk weighted assets), Minimum Capital Adequacy with Capital Buffer Ratio	8.50%	8.50%
Tier I capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions	$ 144,561	$ 141,489
Tier I capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio	0.08	0.08
Common Equity Tier 1 Capital (to risk-weighted assets)	$ 340,621	$ 335,859
Common Equity Tier 1 capital (to risk-weighted assets) Ratio	0.1885	0.1899
Common Equity Tier I capital (to risk weighted assets), For Capital Adequacy Purposes	$ 81,320	$ 79,587
Common Equity Tier I capital (to risk-weighted), For Capital Adequacy Ratio	0.045	0.045
Common Equity Tier I capital (to risk weighted assets) Minimum Capital Adequacy with Capital Buffer	$ 126,490	$ 123,803
Common Equity Tier I capital (to risk weighted), Minimum Capital Adequacy with Capital Buffer Ratio	7.00%	7.00%
Common Equity Tier I capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions	$ 117,456	$ 114,960
Common Equity Tier I capital (to risk-weighted) , To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio	0.065	0.065
Tier I capital (to average assets)	$ 340,621	$ 335,859
Tier I capital (to average assets) Ratio	0.1496	0.1562
Tier I capital (to average assets), For Capital Adequacy Purposes	$ 91,080	$ 86,007
Tier I capital (to average assets), For Capital Adequacy Ratio	0.04	0.04
Amount of minimum Tier 1 leverage capital categorized as well capitalized as defined by regulatory framework for prompt corrective action.	$ 113,844	$ 107,509
Tier I capital (to average assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Ratio	0.05	0.05
State of Wisconsin (to total assets)	$ 340,621	$ 335,859
State of Wisconsin (to total assets) Ratio	15.20%	15.20%
State of Wisconsin (to total assets), For Capital Adequacy Purposes	$ 134,460	$ 132,576
State of Wisconsin (to total assets), For Capital Adequacy Ratio	6.00%	6.00%