Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Restricted stock units vested, net of taxes	Performance-based restricted stock units vested, net of taxes	Total common shareholders’ equity	Total common shareholders’ equity Restricted stock units vested, net of taxes	Total common shareholders’ equity Performance-based restricted stock units vested, net of taxes	Common stock	Common stock Restricted stock units vested, net of taxes	Common stock Performance-based restricted stock units vested, net of taxes	Additional paid-in capital	Additional paid-in capital Restricted stock units vested, net of taxes	Additional paid-in capital Performance-based restricted stock units vested, net of taxes	Retained earnings	Accumulated other comprehensive loss, net	Noncontrolling interest
Beginning balance at Dec. 31, 2023	$ 1,454,887			$ 1,454,794			$ 46,849			$ 864,258			$ 678,412	$ (134,725)	$ 93
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to FB Financial Corporation and noncontrolling interest	78,157			78,149									78,149		8
Other comprehensive income, net of taxes	59,855			59,855										59,855
Repurchase of common stock	(12,699)			(12,699)			(353)			(12,346)
Stock-based compensation expense	7,261			7,261			5			7,256
Restricted stock units and performance-based restricted stock units vested, net of taxes		$ (1,443)	$ (344)		$ (1,443)	$ (344)		$ 106	$ 30		$ (1,549)	$ (374)
Shares issued under employee stock purchase program	882			882			21			861
Dividends declared	(24,126)			(24,126)									(24,126)
Noncontrolling interest distribution	(8)														(8)
Ending balance at Sep. 30, 2024	1,562,422			1,562,329			46,658			858,106			732,435	(74,870)	93
Beginning balance at Jun. 30, 2024	1,500,595			1,500,502			46,643			855,391			730,242	(131,774)	93
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to FB Financial Corporation and noncontrolling interest	10,220			10,220									10,220
Other comprehensive income, net of taxes	56,904			56,904										56,904
Stock-based compensation expense	2,351			2,351			1			2,350
Restricted stock units and performance-based restricted stock units vested, net of taxes		(104)			(104)			4			(108)
Shares issued under employee stock purchase program	483			483			10			473
Dividends declared	(8,027)			(8,027)									(8,027)
Ending balance at Sep. 30, 2024	1,562,422			1,562,329			46,658			858,106			732,435	(74,870)	93
Beginning balance at Dec. 31, 2024	1,567,631			1,567,538			46,663			860,266			762,293	(101,684)	93
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to FB Financial Corporation and noncontrolling interest	65,653			65,645									65,645		8
Other comprehensive income, net of taxes	63,206			63,206										63,206
Common stock issued in connection with acquisition of Southern States Bancshares, Inc. (See Note 2)	368,028			368,028			8,124			359,904
Repurchase of common stock	(68,013)			(68,013)			(1,514)			(66,499)
Stock-based compensation expense	11,567			11,567			5			11,562
Restricted stock units and performance-based restricted stock units vested, net of taxes		(2,166)	$ (621)		(2,166)	$ (621)		129	$ 33		(2,295)	$ (654)
Shares issued under employee stock purchase program	897			897			17			880
Dividends declared	(28,038)			(28,038)									(28,038)
Noncontrolling interest distribution	(8)														(8)
Ending balance at Sep. 30, 2025	1,978,136			1,978,043			53,457			1,163,164			799,900	(38,478)	93
Beginning balance at Jun. 30, 2025	1,611,223			1,611,130			45,808			822,548			786,785	(44,011)	93
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to FB Financial Corporation and noncontrolling interest	23,375			23,375									23,375
Other comprehensive income, net of taxes	5,533			5,533										5,533
Common stock issued in connection with acquisition of Southern States Bancshares, Inc. (See Note 2)	368,028			368,028			8,124			359,904
Repurchase of common stock	(23,867)			(23,867)			(494)			(23,373)
Stock-based compensation expense	3,754			3,754			1			3,753
Restricted stock units and performance-based restricted stock units vested, net of taxes		$ (123)			$ (123)			$ 9			$ (132)
Shares issued under employee stock purchase program	473			473			9			464
Dividends declared	(10,260)			(10,260)									(10,260)
Ending balance at Sep. 30, 2025	$ 1,978,136			$ 1,978,043			$ 53,457			$ 1,163,164			$ 799,900	$ (38,478)	$ 93