Segment Reporting - Schedule of Segment Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Interest income	$ 833,926	$ 725,538	$ 678,410
Interest expense	317,826	309,035	271,193
Net interest income	516,100	416,503	407,217
Provisions for (reversals of) credit losses	43,278	12,004	2,539
Net interest income after provision for credit losses	472,822	404,499	404,678
Mortgage banking income	52,444	46,634	44,692
Other noninterest (loss) income	(8,534)	(7,564)	25,851
Total noninterest (loss) income	43,910	39,070	70,543
Salaries, commissions and employee benefits	217,721	183,813	203,441
Merger and integration costs	23,803	0	0
Depreciation and amortization	12,054	11,966	11,180
Amortization of intangibles	5,298	2,947	3,659
Other noninterest expense	119,338	98,173	106,649
Total noninterest expense	378,214	296,899	324,929
Income before income taxes	138,518	146,670	150,292
Income tax expense	15,880	30,619	30,052
Net income applicable to FB Financial Corporation and noncontrolling interest	122,638	116,051	120,240
Net income applicable to noncontrolling interest	16	16	16
Net income applicable to FB Financial Corporation	122,622	116,035	120,224
Total assets	16,300,292	13,157,482	12,604,403
Goodwill	350,353	242,561	242,561
Banking
Segment Reporting Information [Line Items]
Interest income	829,150	726,033	678,591
Interest expense	323,058	315,250	277,342
Net interest income	506,092	410,783	401,249
Provisions for (reversals of) credit losses	37,637	12,264	2,599
Net interest income after provision for credit losses	468,455	398,519	398,650
Mortgage banking income	0	0	0
Other noninterest (loss) income	(8,775)	(8,376)	25,831
Total noninterest (loss) income	(8,775)	(8,376)	25,831
Salaries, commissions and employee benefits	187,473	154,810	170,975
Merger and integration costs	23,803
Depreciation and amortization	11,980	11,541	10,444
Amortization of intangibles	5,298	2,947	3,659
Other noninterest expense	96,210	77,192	85,491
Total noninterest expense	324,764	246,490	270,569
Income before income taxes	134,916	143,653	153,912
Total assets	15,623,962	12,554,435	12,050,245
Goodwill	350,353	242,561	242,561
Mortgage
Segment Reporting Information [Line Items]
Interest income	4,776	(495)	(181)
Interest expense	(5,232)	(6,215)	(6,149)
Net interest income	10,008	5,720	5,968
Provisions for (reversals of) credit losses	5,641	(260)	(60)
Net interest income after provision for credit losses	4,367	5,980	6,028
Mortgage banking income	52,444	46,634	44,692
Other noninterest (loss) income	241	812	20
Total noninterest (loss) income	52,685	47,446	44,712
Salaries, commissions and employee benefits	30,248	29,003	32,466
Merger and integration costs	0
Depreciation and amortization	74	425	736
Amortization of intangibles	0	0	0
Other noninterest expense	23,128	20,981	21,158
Total noninterest expense	53,450	50,409	54,360
Income before income taxes	3,602	3,017	(3,620)
Total assets	676,330	603,047	554,158
Goodwill	$ 0	$ 0	$ 0

FB Financial Corp 10-K