Minimum Capital Requirements (Details) $ in Thousands	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
FB Financial Corporation
Total Capital (to risk-weighted assets)
Actual, Amount	$ 1,456,669	$ 1,434,581
Actual, Ratio	0.142	0.145
Minimum Capital adequacy with capital buffer, Amount	$ 1,077,296	$ 1,039,984
Minimum Capital adequacy with capital buffer, Ratio	0.105	0.105
Tier 1 Capital (to risk-weighted assets)
Actual, Amount	$ 1,264,358	$ 1,251,874
Actual, Ratio	0.123	0.126
Minimum Capital adequacy with capital buffer, Amount	$ 872,096	$ 841,892
Minimum Capital adequacy with capital buffer, Ratio	8.50%	8.50%
Tier 1 Capital (to average assets)
Actual, Amount	$ 1,264,358	$ 1,251,874
Actual, Ratio	0.102	0.105
Minimum Capital adequacy with capital buffer, Amount	$ 497,942	$ 474,831
Minimum Capital adequacy with capital buffer. Ratio	0.040	0.040
Common Equity Tier 1 Capital (to risk-weighted assets)
Actual, Amount	$ 1,234,358	$ 1,221,874
Actual Ratio	12.00%	12.30%
Minimum Capital adequacy with capital buffer, Amount	$ 718,197	$ 693,322
Minimum Capital adequacy with capital buffer, Ratio	0.070	0.070
FirstBank
Total Capital (to risk-weighted assets)
Actual, Amount	$ 1,413,849	$ 1,396,407
Actual, Ratio	0.138	0.141
Minimum Capital adequacy with capital buffer, Amount	$ 1,075,838	$ 1,038,760
Minimum Capital adequacy with capital buffer, Ratio	0.105	0.105
To be well capitalized under prompt corrective action provisions, Amount	$ 1,024,608	$ 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	$ 1,221,538	$ 1,213,700
Actual, Ratio	0.119	0.123
Minimum Capital adequacy with capital buffer, Amount	$ 870,917	$ 840,901
Minimum Capital adequacy with capital buffer, Ratio	8.50%	8.50%
To be well capitalized under prompt corrective action provisions, Amount	$ 819,686	$ 791,436
To be well capitalized under prompt corrective action provisions, Ratio	0.080	0.080
Tier 1 Capital (to average assets)
Actual, Amount	$ 1,221,538	$ 1,213,700
Actual, Ratio	0.098	0.102
Minimum Capital adequacy with capital buffer, Amount	$ 497,337	$ 474,044
Minimum Capital adequacy with capital buffer. Ratio	0.040	0.040
To be well capitalized under prompt corrective action provisions, Amount	$ 621,671	$ 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	$ 1,221,538	$ 1,213,700
Actual Ratio	11.90%	12.30%
Minimum Capital adequacy with capital buffer, Amount	$ 717,226	$ 692,507
Minimum Capital adequacy with capital buffer, Ratio	0.070	0.070
To be well capitalized under prompt corrective action provisions, Amount	$ 665,995	$ 643,042
To be well capitalized under prompt corrective action provisions, Ratio	6.50%	6.50%