Other Real Estate Owned - Summary of Other Real Estate Owned (Parenthetical) (Details) $ in Thousands	Jul. 31, 2017 USD ($)
Clayton Banks
Real Estate Properties [Line Items]
Acquired excess facilities held for sale	$ 4,147

Business combination recognized identifiable assets acquired and liabilities assumed excess facilities acquired held for sale.

No definition available.

Name:	fbk_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedExcessFacilitiesAcquiredHeldForSale
Namespace Prefix:	fbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant