Investment Securities - Schedule of Other Than Temporary Impairment, Credit Losses Recognized In Earnings (Details) $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($)
Investments Debt And Equity Securities [Abstract]
Additions related to credit losses for which OTTI was not previously recognized	$ (945)
Balance as of September 30, 2017	$ (945)

Other than temporary impairment credit losses recognized in earnings from equity securities additions no previous impairment.

No definition available.

Name:	fbk_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsFromEquitySecuritiesAdditionsNoPreviousImpairment
Namespace Prefix:	fbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration