Name:	fbk_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferOrServicingAssetsOrLiabilitiesImpactOfOnePercentAdverseChangeInDiscountRate
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Sensitivity analysis of fair value of interests continued to be held by transferor servicing assets or liabilities impact of two percent adverse change in discount rate.

No definition available.

Name:	fbk_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferOrServicingAssetsOrLiabilitiesImpactOfTwoPercentAdverseChangeInDiscountRate
Namespace Prefix:	fbk_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Servicing assets and servicing liabilities at fair value assumptions used to estimate fair value weighted average coupon interest rate.

No definition available.

Name:	fbk_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueWeightedAverageCouponInterestRate
Namespace Prefix:	fbk_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

Servicing assets and servicing liabilities at fair value assumptions used to estimate fair value weighted average servicing fee.

No definition available.

Name:	fbk_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueWeightedAverageServicingFee
Namespace Prefix:	fbk_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
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Weighted average life of securitized assets regardless of when the transfer occurred, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481326/860-20-50-4

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Discount rate which is used to value residual cash flows generated by financial assets of a securitization, asset-backed financing arrangement, or similar transfer regardless of when the transfer occurred.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481326/860-20-50-4

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Period Type:	duration

Estimated rate of prepayment of principal on financial assets regardless of when the transfer occurred.

Name:	us-gaap_AssumptionForFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesPrepaymentSpeed
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Principal amount of transferred financial assets in which the transferor has continuing involvement with the assets underlying the transaction. Continuing involvement includes, but is not limited to, servicing, recourse, and restrictions on transferor's interests in transferred financial assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481326/860-20-50-4

Name:	us-gaap_ContinuingInvolvementWithTransferredFinancialAssetsPrincipalAmountOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481326/860-20-50-4

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

Name:	us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInPrepaymentSpeed
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Period Type:	instant

- References

No definition available.