Consolidated statements of changes in shareholders' equity (Unaudited) (Parenthetical) $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($)
Statement Of Stockholders Equity [Abstract]
Fair Value Election on Mortgage Servicing Rights Retained Earnings Adjustment, Tax	$ 396

Fair value election on mortgage servicing rights retained earnings adjustment, tax.

No definition available.

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