Entity tax identification number Entity Tax Identification Number Rollovers EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Maximum Maximum [Member] Forfeited nonvested account, decrease from plan expenses EBP, Forfeited Nonvested Account, Decrease from Administrative Expense Legal Entity [Axis] Legal Entity [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] EBP, Description of Plan [Table] EBP, Description of Plan [Table] Mutual funds Mutual Fund [Member] EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Table] Total deductions EBP, Change in Net Asset Available for Benefit, Decrease Fair Value Measurements EBP, Investment, Fair Value and NAV [Text Block] Participant loans acquired, interest rate EBP, Assets Acquired and Held for Investment, Participant Loan, Interest Rate EBP, Assets Acquired and Held for Investment, Participant Loan, Interest Rate Total investments at fair value EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Level 1 Fair Value, Inputs, Level 1 [Member] EBP, Investment, Fair Value and NAV [Abstract] Vesting period EBP, Employer Contribution Vesting Service Period EBP, Employer Contribution Vesting Service Period Assets EBP, Asset [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Additions EBP, Change in Net Asset Available for Benefit, Increase [Abstract] EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Payment of benefits EBP, Payment to Participant [Policy Text Block] Amendment Flag Amendment Flag Basis of accounting EBP, Basis of Accounting [Policy Text Block] EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Table] Plan Sponsor's common stock (in shares) EBP, Investment, Number of Shares EBP, Description of Plan and Accounting Change [Abstract] Receivables: EBP, Receivable [Abstract] EBP, Investment, Fair Value and NAV EBP, Investment, Fair Value and NAV [Table Text Block] EBP, Contingency [Table] EBP, Contingency [Table] EBP, Tranche 2 EBP, Employer Matching Contribution, Tranche Two [Member] EBP, Employer Matching Contribution, Tranche Two EBP, Contribution, Participating Employer [Domain] EBP, Contribution, Participating Employer [Domain] EBP, Contingency [Abstract] FB Financial Corporation common stock Common Stock [Member] Investments [Domain] Investments [Domain] Use of estimates EBP, Use of Estimate [Policy Text Block] Schedule H, Line 4i – Schedule of Assets (Held At End of Year) EBP, Schedule of Asset Held for Investment [Text Block] Cover [Abstract] EBP, Contribution, Participating Employer [Axis] EBP, Contribution, Participating Employer [Axis] Risks and Uncertainties EBP, Risk and Uncertainty [Text Block] Employer EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Minimum Minimum [Member] Interest income on notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Investment Type [Axis] Investment Type [Axis] Total contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Participants EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Interest and dividends EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment EBP, Description of Plan [Line Items] EBP, Description of Plan [Line Items] Plan number EBP, Plan Number EBP, Investment, Fair Value and NAV [Line Items] EBP, Investment, Fair Value and NAV [Line Items] Description of the Plan EBP, Description of Plan [Text Block] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] Contributions EBP, Contribution [Policy Text Block] Employer, Common Stock EBP, Employer, Common Stock [Member] EBP, Schedule of Asset Held for Investment [Abstract] EBP, Accounting Policy [Table] EBP, Accounting Policy [Table] Total additions EBP, Change in Net Asset Available for Benefit, Increase Cash Cash Reserve Account Cash [Member] Investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Investment, Identifier [Axis] Investment, Identifier [Axis] Administrative expenses EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Assets held for investment EBP, Asset Held for Investment Document Information [Line Items] Document Information [Line Items] EBP, Risk and Uncertainty [Line Items] EBP, Risk and Uncertainty [Line Items] EBP, Risk and Uncertainty [Table] EBP, Risk and Uncertainty [Table] Participant compensation matched, percentage EBP, Employer Contribution, Participant Compensation Matched, Percentage EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Level 2 Fair Value, Inputs, Level 2 [Member] Participant investment in Plan Sponsor's common stock, percentage (up to) EBP, Participant Maximum Investment in Employer Stock, Percentage EBP, Participant Maximum Investment in Employer Stock, Percentage EBP, Tax Status [Table] EBP, Tax Status [Table] Net increase EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Related Parties and Parties-In-Interest Transactions EBP, Related Party and Party-in-Interest Transactions [Text Block] EBP, Related Party and Party-in-Interest Transactions [Abstract] EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] Receivables EBP, Receivable Employer contributions EBP, Employer Contribution, Receivable Automatic deferral rate EBP, Participant Contribution, Automatic, Deferral Rate Investments at fair value: EBP, Investment, Fair Value [Abstract] Dividend income EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment Benefits paid to participants EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Current value EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Vesting percentage EBP, Employer Contribution Vesting Percentage EBP, Employer Contribution Vesting Percentage EBP, Statement of Net Asset Available for Benefit [Abstract] EBP, Accounting Policy [Line Items] EBP, Accounting Policy [Line Items] EBP, Tax Status [Abstract] Expenses EBP, Expense [Policy Text Block] Investment valuation and income recognition EBP, Investment [Policy Text Block] Level 1, Level 2, and Level 3 Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Document Type Document Type Plan Termination EBP, Plan Termination [Text Block] Entity Central Index Key Entity Central Index Key Participant loans, interest rate EBP, Asset Held for Investment, Participant Loan, Interest Rate EBP, Risk and Uncertainty [Abstract] EBP, Tax Status [Line Items] EBP, Tax Status [Line Items] EBP 001 EBP 001 [Member] EBP 001 EBP, Subsequent Event [Table] EBP, Subsequent Event [Table] Deductions EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Forfeited nonvested account, decrease from employer contribution EBP, Forfeited Nonvested Account, Decrease from Employer Contribution Notes receivable from participants EBP, Note Receivable from Participant Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Summary of Significant Accounting Policies EBP, Summary of Accounting Policy [Text Block] Entity Registrant Name Entity Registrant Name Participant plan qualification, service period, full-time EBP, Requisite Service Period, Full-Time EBP, Requisite Service Period, Full-Time EBP, Subsequent Event [Abstract] Subsequent Events EBP, Subsequent Event [Text Block] Income Tax Status EBP, Tax Status [Text Block] EBP, Tranche 1 EBP, Employer Matching Contribution, Tranche One [Member] EBP, Employer Matching Contribution, Tranche One Payments to affiliate EBP, Related Party Transaction EBP, Related Party Transaction EBP, Subsequent Event [Line Items] EBP, Subsequent Event [Line Items] EBP, Contingency [Line Items] EBP, Contingency [Line Items] Document Information [Table] Document Information [Table] Notes receivable from participants EBP, Note Receivable from Participant [Policy Text Block] Total investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Participant plan qualification, service period, part-time EBP, Requisite Service Period, Part-Time EBP, Requisite Service Period, Part-Time EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Line Items] Level 3 Fair Value, Inputs, Level 3 [Member] Other receivables EBP, Other Receivable Net assets available for benefits Net assets available for benefits, beginning of year Net assets available for benefits, end of year EBP, Net Asset Available for Benefit Entity [Domain] Entity [Domain] Contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Forfeited nonvested account EBP, Forfeited Nonvested Account Employer matching percentage EBP, Employer Contribution, Matching Percentage Automatic deferral rate, annual increase EBP, Participant Contribution, Automatic, Annual Increase Deferral Rate EBP, Participant Contribution, Automatic, Annual Increase Deferral Rate EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Line Items]