Income, Related Party

No definition available.

Name:	fbk_IncomeRelatedParty
Namespace Prefix:	fbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI) and investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI https://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740

+ Details

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

- Definition

Amount of operating lease expense. Excludes sublease income.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 4
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123391704&loc=SL77918638-209977

+ Details

Name:	us-gaap_OperatingLeaseExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

+ References

No definition available.

+ Details

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

- Definition

Amount of deposits held by the entity for a related party (entity, shareholder, employee).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_PreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_DirectorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=fbk_FBKAviationLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=fbk_AviationTimeSharingAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_UnfundedLoanCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=fbk_CertainExecutiveOfficersCertainManagementAndDirectorsAndTheirAssociatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related Party Transactions - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Related Party Transaction [Line Items]
Deposits from related parties	$ 336,448		$ 347,660
Preferred Stock
Related Party Transaction [Line Items]
Equity security without readily determinable market value	10,000		10,000
Directors
Related Party Transaction [Line Items]
Operating lease expense	90	$ 101
Directors \| FBK Aviation, LLC \| Aviation Time Sharing Agreements
Related Party Transaction [Line Items]
Income from related party	7	$ 11
Unfunded Loan Commitment \| Certain Executive Officers, Certain Management and Directors and Their Associates
Related Party Transaction [Line Items]
Unfunded commitments	$ 34,089		$ 31,564