| In millions, except per share items | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Cash flows from operating activities: | | | | | | | | |
| Net income attributable to FB Financial Corporation and noncontrolling interest | 190.3 | 63.6 | 83.8 | 80.2 | 52.4 | 40.6 | | |
| Adjustments to reconcile net income to net cash from operating activities: | | | | | | | | |
| Depreciation and amortization of fixed assets and software | 8.4 | 7.5 | 5.2 | 4.3 | 6.3 | 4.0 | 3.3 | 3.1 |
| Amortization of core deposit and other intangibles | 5.5 | 5.3 | 4.3 | 3.2 | | | | |
| Capitalization of mortgage servicing rights | -39.0 | -47.0 | -42.2 | -54.9 | -59.0 | -46.1 | -26.5 | -6.4 |
| Net change in fair value of mortgage servicing rights | 3.5 | 47.7 | 26.3 | 2.8 | 4.0 | | | |
| Stock-based compensation expense | 10.3 | 10.2 | 7.1 | 7.2 | 6.8 | 4.7 | | |
| Provision for credit losses on unfunded commitments | -2.0 | 13.4 | | | | | | |
| Provision for mortgage loan repurchases | -0.8 | 2.6 | 0.4 | 0.2 | 0.8 | 0.5 | 1.4 | 0.2 |
| Amortization of premiums and accretion of discounts on securities, net | 8.8 | 7.4 | 3.0 | 2.8 | 2.7 | 2.3 | 1.5 | 1.4 |
| Originations of loans held for sale | -6,300.9 | -6,650.3 | -4,540.7 | -5,958.1 | -6,331.5 | -4,671.6 | -2,757.5 | -1,156.2 |
| Proceeds from sale of loans held for sale | 6,387.1 | 6,487.8 | 4,662.7 | 6,260.5 | 6,408.2 | 4,534.8 | 2,739.9 | 1,047.9 |
| Gain on sale and change in fair value of loans held for sale | -162.0 | -270.8 | -100.2 | -88.7 | -107.2 | -115.5 | -65.9 | -30.6 |
| Net (gain) loss on write-downs of other real estate owned and other assets | -2.5 | 1.5 | -0.5 | 0.1 | -0.8 | -1.3 | 0.3 | -0.1 |
| Provision for deferred income taxes | 30.8 | -25.5 | -1.9 | 6.4 | 6.5 | 9.3 | 1.6 | 0.8 |
| Changes in: | | | | | | | | |
| Other assets and interest receivable | | | | -23.0 | 6.5 | -24.7 | -1.3 | -5.5 |
| Accrued expenses and other liabilities | -100.1 | 43.5 | 13.0 | -16.1 | 47.6 | 15.3 | 12.8 | 10.1 |
| Net cash provided by operating activities | 54.9 | -270.0 | 63.9 | 212.2 | 37.6 | -245.2 | | |
| |
| Cash flows from investing activities: | | | | | | | | |
| Activity in available-for-sale securities: | | | | | | | | |
| Sales | 314.0 | 513.5 | 162.0 | 75.8 | 178.1 | 375.5 | 297.8 | 153.3 |
| Maturities, prepayments and calls | 296.3 | 220.5 | 113.0 | 73.1 | 83.3 | 104.4 | 103.2 | 84.4 |
| Purchases | -847.2 | -425.0 | -151.4 | -203.8 | -81.4 | -316.4 | -164.9 | -109.7 |
| Net change in loans | -457.0 | 4.4 | -365.0 | | | -127.9 | -206.7 | -73.1 |
| Purchases of FHLB stock | -5.3 | -0.5 | -2.5 | | | | | |
| Purchases of premises and equipment | -6.1 | -5.9 | -6.8 | -10.1 | -4.5 | -4.8 | -5.9 | -5.4 |
| Proceeds from the sale of premises and equipment | | | 1.3 | 0.4 | 0.0 | 0.0 | 0.0 | 0.6 |
| Proceeds from the sale of other real estate owned | 9.4 | 6.9 | 3.9 | 4.8 | 5.4 | 6.7 | 3.8 | |
| Net cash provided by (used in) investing activities | -849.6 | 310.1 | -182.9 | -586.5 | -267.2 | -32.7 | | |
| |
| Cash flows from financing activities: | | | | | | | | |
| Share based compensation withholding payments | -10.2 | -1.5 | -6.1 | -2.7 | | | | |
| Net proceeds from sale of common stock under employee stock purchase program | 1.5 | 1.0 | 0.8 | 1.2 | 153.4 | 116.1 | | |
| Net cash used in financing activities | 1,274.5 | 1,045.1 | 226.3 | 379.9 | 213.0 | 316.5 | | |
| Net change in cash and cash equivalents | 479.8 | 1,085.2 | 107.3 | 5.6 | -16.6 | | | |
| |
| Supplemental cash flow information: | | | | | | | | |
| Interest paid | 41.2 | 48.7 | 55.1 | 32.0 | 15.5 | 9.5 | 9.0 | 9.7 |
| Supplemental noncash disclosures: | | | | | | | | |
| Transfers from loans to other real estate owned | 5.3 | 2.7 | 5.5 | 2.1 | 3.6 | 2.7 | 4.1 | |
| Transfers from loans to loans held for sale | 10.4 | 11.5 | 8.0 | 11.9 | | | | |
| Transfers from loans held for sale to loans | 86.3 | 55.8 | 12.3 | 14.7 | 11.7 | 18.0 | 5.0 | 5.1 |
| Right-of-use assets obtained in exchange for operating lease liabilities | 1.0 | 2.4 | 37.9 | | | | | |