Consolidated statements of changes in shareholders' equity - USD ($) $ in Thousands	Total	Cumulative effect adjustment to adopt ASC 326	Adjusted balance	Common stock	Common stock Adjusted balance	Additional paid-in capital	Additional paid-in capital Adjusted balance	Retained earnings	Retained earnings Cumulative effect adjustment to adopt ASC 326	Retained earnings Adjusted balance	Accumulated other comprehensive income, net	Accumulated other comprehensive income, net Adjusted balance	Total common shareholders' equity	Total common shareholders' equity Cumulative effect adjustment to adopt ASC 326	Total common shareholders' equity Adjusted balance	Noncontrolling interests	Noncontrolling interests Adjusted balance
Beginning balance at Dec. 31, 2019	$ 762,329	$ (25,018)	$ 737,311	$ 31,034	$ 31,034	$ 425,633	$ 425,633	$ 293,524	$ (25,018)	$ 268,506	$ 12,138	$ 12,138	$ 762,329	$ (25,018)	$ 737,311	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to FB Financial Corporation and noncontrolling interest	23,618							23,618					23,618
Other comprehensive income, net of taxes	11,751										11,751		11,751
Common stock issued in connection with acquisition of the FNB Financial Corp., net of registration costs (See Note 2)	34,847			955		33,892							34,847
Stock based compensation expense	4,233			11		4,222							4,233
Restricted stock units vested and distributed, net of shares withheld	(1,162)			89		(1,251)							(1,162)
Shares issued under employee stock purchase program	446			12		434							446
Dividends declared	(5,828)							(5,828)					(5,828)
Ending balance at Jun. 30, 2020	805,216			32,101		462,930		286,296			23,889		805,216			0
Beginning balance at Mar. 31, 2020	782,330			32,067		460,938		266,385			22,940		782,330			0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to FB Financial Corporation and noncontrolling interest	22,873							22,873					22,873
Other comprehensive income, net of taxes	949										949		949
Stock based compensation expense	2,350			6		2,344							2,350
Restricted stock units vested and distributed, net of shares withheld	(324)			28		(352)							(324)
Dividends declared	(2,962)							(2,962)					(2,962)
Ending balance at Jun. 30, 2020	805,216			32,101		462,930		286,296			23,889		805,216			0
Beginning balance at Dec. 31, 2020	1,291,382			47,222		898,847		317,625			27,595		1,291,289			93
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to FB Financial Corporation and noncontrolling interest	96,176							96,168					96,168			8
Other comprehensive income, net of taxes	(9,190)										(9,190)		(9,190)
Stock based compensation expense	5,181			5		5,176							5,181
Restricted stock units vested and distributed, net of shares withheld	(1,940)			112		(2,052)							(1,940)
Shares issued under employee stock purchase program	833			22		811							833
Dividends declared	(10,620)							(10,620)					(10,620)
Noncontrolling interest distribution	(8)															(8)
Ending balance at Jun. 30, 2021	1,371,814			47,361		902,782		403,173			18,405		1,371,721			93
Beginning balance at Mar. 31, 2021	1,329,196			47,332		900,521		365,192			16,058		1,329,103			93
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to FB Financial Corporation and noncontrolling interest	43,302							43,294					43,294			8
Other comprehensive income, net of taxes	2,347										2,347		2,347
Stock based compensation expense	2,515			2		2,513							2,515
Restricted stock units vested and distributed, net of shares withheld	(225)			27		(252)							(225)
Shares issued under employee stock purchase program	0
Dividends declared	(5,313)							(5,313)					(5,313)
Noncontrolling interest distribution	(8)															(8)
Ending balance at Jun. 30, 2021	$ 1,371,814			$ 47,361		$ 902,782		$ 403,173			$ 18,405		$ 1,371,721			$ 93