Fair Value of Financial Instruments - Schedule of Changes in Fair Value Associated with Commercial Loans Held for Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Change in fair value:
Fair Value Recurring Basis Unobservable Input Reconciliation Asset Gain Loss Statement Of Income Extensible List Not Disclosed Flag	Changes in valuation included in other noninterest income	Changes in valuation included in other noninterest income
Franklin Financial Network, Inc. | Commercial and industrial | Principal balance
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Carrying value at beginning of period	$ 34,357	$ 86,762
Change in fair value:
Paydowns and payoffs	(28,376)	(43,676)
Write-offs to discount	(5,981)	(8,729)
Changes in valuation included in other noninterest income	0	0
Carrying value at end of period	0	34,357
Franklin Financial Network, Inc. | Commercial and industrial | Fair Value discount
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Carrying value at beginning of period	(3,867)	(7,463)
Change in fair value:
Paydowns and payoffs	0	0
Write-offs to discount	5,981	8,729
Changes in valuation included in other noninterest income	(2,114)	(5,133)
Carrying value at end of period	0	(3,867)
Franklin Financial Network, Inc. | Commercial and industrial |  Fair Value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Carrying value at beginning of period	30,490	79,299
Change in fair value:
Paydowns and payoffs	(28,376)	(43,676)
Write-offs to discount	0	0
Changes in valuation included in other noninterest income	(2,114)	(5,133)
Carrying value at end of period	$ 0	$ 30,490