Parent company financial statements - Income Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income
Dividend income from bank subsidiaries	$ 2,893	$ 2,705	$ 4,051
Loss on other assets	323	(90)	(104)
Net interest income	347,370	265,658	226,036
Interest expense
Interest expense	37,628	48,986	56,501
Other noninterest expense	359,678	364,226	235,326
Net income applicable to FB Financial Corporation	190,285	63,621	83,814
Parent Company
Income
Dividend income from bank subsidiaries	122,500	49,706	0
Dividend income from nonbank subsidiaries	2,525	0	0
Gain on investments	249	217	0
Loss on other assets	0	0	(16)
Other income	15	1,732	211
Net interest income	125,289	51,655	195
Interest expense
Interest expense	2,455	3,122	1,638
Salaries, legal and professional fees	1,445	1,458	1,056
Other noninterest expense	1,812	283	120
Total expenses	5,712	4,863	2,814
Income (loss) before income tax benefit and equity in undistributed earnings of subsidiaries	119,577	46,792	(2,619)
Federal and state income tax benefit	(2,992)	(1,155)	(683)
Income (loss) before equity in undistributed earnings of subsidiaries	122,569	47,947	(1,936)
Equity in undistributed earnings from bank subsidiaries	68,351	15,168	85,750
Equity in undistributed earnings from nonbank subsidiaries	(635)	506	0
Net income applicable to FB Financial Corporation	$ 190,285	$ 63,621	$ 83,814