Loans Held for Investment - Summary of Investment In Loans By Credit Quality Indicators by Year of Origin and Gross Charge-Offs (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
2025	$ 89,293	$ 143,212
2024	115,616	145,098
2023	114,195	123,258
2022	105,805	52,321
2021	44,996	46,407
Prior	149,168	130,752
Revolving Lines	125,862	117,017
Total	744,935	758,065
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2025	88,608	142,907
2024	113,502	141,573
2023	108,764	118,041
2022	100,721	51,178
2021	43,546	45,351
Prior	144,328	127,070
Revolving Lines	123,442	114,058
Total	722,911	740,178
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2025	305	189
2024	37
2023		1,681
2022	309
2021	38
Prior	524	220
Revolving Lines	355
Total	1,568	2,090
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2025	345	42
2024	1,769	3,444
2023	5,431	3,526
2022	4,775	1,129
2021	1,412	1,056
Prior	4,316	3,462
Revolving Lines	1,956	2,838
Total	20,004	15,497
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2025	35	74
2024	308	81
2023		10
2022		14
Revolving Lines	109	121
Total	452	300
Gross charge-offs
Financing Receivable, Credit Quality Indicator [Line Items]
2025	4
2024	285	123
2023	310	374
2022	127	45
2021	137	178
Prior		21
Revolving Lines	986	920
Total	1,849	1,661
1-4 Family Residential
Financing Receivable, Credit Quality Indicator [Line Items]
2025	6,869	15,139
2024	15,708	65,145
2023	60,919	70,052
2022	60,624	31,886
2021	26,101	22,252
Prior	60,522	50,168
Total	230,743	254,642
1-4 Family Residential \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2025	6,660	15,139
2024	15,559	61,966
2023	55,859	66,541
2022	57,454	30,758
2021	24,825	22,112
Prior	57,911	47,915
Total	218,268	244,431
1-4 Family Residential \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2023		257
2022	252
Prior	74	32
Total	326	289
1-4 Family Residential \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2025	209
2024	149	3,179
2023	5,060	3,254
2022	2,918	1,128
2021	1,276	140
Prior	2,537	2,221
Total	12,149	9,922
Residential Construction
Financing Receivable, Credit Quality Indicator [Line Items]
2025	23,340	23,044
2024	13,714	11,095
2023	1,004
Total	38,058	34,139
Residential Construction \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2025	23,340	23,044
2024	13,714	11,095
2023	1,004
Total	38,058	34,139
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2025	30,142	50,394
2024	57,298	47,231
2023	37,019	40,122
2022	36,848	11,240
2021	10,683	18,086
Prior	76,754	73,990
Total	248,744	241,063
Commercial Real Estate \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2025	30,067	50,394
2024	55,678	47,231
2023	37,019	40,122
2022	36,848	11,240
2021	10,683	17,629
Prior	76,108	73,990
Total	246,403	240,606
Commercial Real Estate \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2025	75
Prior	212
Total	287
Commercial Real Estate \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2024	1,620
2021		457
Prior	434
Total	2,054	457
Other Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2025	19,183	39,571
2024	19,863	4,306
2023	3,339	7,757
2022	5,763	8,062
2021	7,438	5,500
Prior	11,208	5,565
Revolving Lines	25,405	24,220
Total	92,199	94,981
Other Commercial \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2025	19,115	39,529
2024	19,523	4,011
2023	3,169	6,107
2022	3,849	8,062
2021	7,310	5,041
Prior	9,628	4,138
Revolving Lines	24,304	23,556
Total	86,898	90,444
Other Commercial \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2025	43
2024	32
2023		1,424
2022	57
2021	38
Prior	238	188
Revolving Lines	354
Total	762	1,612
Other Commercial \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2025		42
2024		250
2023	170	226
2022	1,857
2021	90	459
Prior	1,342	1,239
Revolving Lines	638	566
Total	4,097	2,782
Other Commercial \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2025	25
2024	308	45
Revolving Lines	109	98
Total	442	143
Home Equity
Financing Receivable, Credit Quality Indicator [Line Items]
2025	2,454	4,592
2024	3,832	7,597
2023	6,576	1,689
2022	1,331	73
2021	49	62
Prior	684	1,022
Revolving Lines	97,478	91,515
Total	112,404	106,550
Home Equity \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2025	2,162	4,592
2024	3,832	7,597
2023	6,576	1,643
2022	1,331	73
2021	49	62
Prior	681	1,020
Revolving Lines	96,160	89,267
Total	110,791	104,254
Home Equity \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2025	156
Total	156
Home Equity \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2025	136
2023		46
Prior	3	2
Revolving Lines	1,318	2,225
Total	1,457	2,273
Home Equity \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Lines		23
Total		23
Other Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2025	7,305	10,472
2024	5,201	9,724
2023	5,338	3,638
2022	1,239	1,060
2021	725	507
Prior		7
Revolving Lines	2,979	1,282
Total	22,787	26,690
Other Consumer \| Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2025	7,264	10,209
2024	5,196	9,673
2023	5,137	3,628
2022	1,239	1,045
2021	679	507
Prior		7
Revolving Lines	2,978	1,235
Total	22,493	26,304
Other Consumer \| Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2025	31	189
2024	5
Revolving Lines	1
Total	37	189
Other Consumer \| Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2024		15
2023	201
2022		1
2021	46
Revolving Lines		47
Total	247	63
Other Consumer \| Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2025	10	74
2024		36
2023		10
2022		14
Total	$ 10	$ 134

FB Bancorp, Inc. /MD/ 10-K