Minimum Capital Requirements (Details) $ in Thousands	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
FB Financial Corporation
Total Capital (to risk-weighted assets)
Actual, Amount	$ 1,501,110	$ 1,434,581
Actual, Ratio	0.130	0.145
Minimum Capital adequacy with capital buffer, Amount	$ 1,210,236	$ 1,039,984
Minimum Capital adequacy with capital buffer, Ratio	0.105	0.105
Tier 1 Capital (to risk-weighted assets)
Actual, Amount	$ 1,287,489	$ 1,251,874
Actual, Ratio	0.112	0.126
Minimum Capital adequacy with capital buffer, Amount	$ 979,715	$ 841,892
Minimum Capital adequacy with capital buffer, Ratio	8.50%	8.50%
Tier 1 Capital (to average assets)
Actual, Amount	$ 1,287,489	$ 1,251,874
Actual, Ratio	0.107	0.105
Minimum Capital adequacy with capital buffer, Amount	$ 479,489	$ 474,831
Minimum Capital adequacy with capital buffer. Ratio	0.040	0.040
Common Equity Tier 1 Capital (to risk-weighted assets)
Actual, Amount	$ 1,257,489	$ 1,221,874
Actual Ratio	10.90%	12.30%
Minimum Capital adequacy with capital buffer, Amount	$ 806,824	$ 693,322
Minimum Capital adequacy with capital buffer, Ratio	0.070	0.070
FirstBank
Total Capital (to risk-weighted assets)
Actual, Amount	$ 1,472,955	$ 1,396,407
Actual, Ratio	0.128	0.141
Minimum Capital adequacy with capital buffer, Amount	$ 1,208,502	$ 1,038,760
Minimum Capital adequacy with capital buffer, Ratio	0.105	0.105
To be well capitalized under prompt corrective action provisions, Amount	$ 1,150,954	$ 989,295
To be well capitalized under prompt corrective action provisions, Ratio	0.100	0.100
Tier 1 Capital (to risk-weighted assets)
Actual, Amount	$ 1,259,334	$ 1,213,700
Actual, Ratio	0.109	0.123
Minimum Capital adequacy with capital buffer, Amount	$ 978,311	$ 840,901
Minimum Capital adequacy with capital buffer, Ratio	8.50%	8.50%
To be well capitalized under prompt corrective action provisions, Amount	$ 920,764	$ 791,436
To be well capitalized under prompt corrective action provisions, Ratio	0.080	0.080
Tier 1 Capital (to average assets)
Actual, Amount	$ 1,259,334	$ 1,213,700
Actual, Ratio	0.105	0.102
Minimum Capital adequacy with capital buffer, Amount	$ 479,290	$ 474,044
Minimum Capital adequacy with capital buffer. Ratio	0.040	0.040
To be well capitalized under prompt corrective action provisions, Amount	$ 599,113	$ 592,555
To be well capitalized under prompt corrective action provisions, Ratio	0.050	0.050
Common Equity Tier 1 Capital (to risk-weighted assets)
Actual, Amount	$ 1,259,334	$ 1,213,700
Actual Ratio	10.90%	12.30%
Minimum Capital adequacy with capital buffer, Amount	$ 805,668	$ 692,507
Minimum Capital adequacy with capital buffer, Ratio	0.070	0.070
To be well capitalized under prompt corrective action provisions, Amount	$ 748,120	$ 643,042
To be well capitalized under prompt corrective action provisions, Ratio	6.50%	6.50%