Consolidated statements of comprehensive income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 45,290	$ (5,599)	$ 141,466	$ 18,019
Other comprehensive income (loss), net of tax:
Net change in unrealized gain in available-for-sale securities, net of tax (benefits) expenses of $(2,054), $521, $(4,708) and $5,225	(5,818)	1,788	(15,380)	15,091
Reclassification adjustment for gain on sale of securities included in net income, net of tax expenses of $19, $137, $23 and $137	(56)	(387)	(67)	(387)
Net change in unrealized loss in hedging activities, net of tax expenses (benefits) of $38, $40, $173 and $(403)	106	112	489	(1,145)
Reclassification adjustment for gain on hedging activities, net of tax expenses of $0, $41, $0 and $145	0	(115)	0	(410)
Total other comprehensive (loss) income, net of tax	(5,768)	1,398	(14,958)	13,149
Comprehensive income (loss)	39,522	(4,201)	126,508	31,168
Comprehensive income applicable to noncontrolling interests	0	0	8	0
Comprehensive income (loss) applicable to FB Financial Corporation	$ 39,522	$ (4,201)	$ 126,500	$ 31,168