Stock-Based Compensation - Summary of Vested and Unvested Restricted Stock Units Outstanding (Details) - $ / shares	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Aug. 15, 2020
Franklin Financial Network, Inc.
Weighted Average Grant Date Fair Value
Replacement awards issued to employees (in shares)			118,776
Restricted Stock Units (RSUs)
Restricted Stock Units Outstanding
Restricted Stock Units Outstanding, Balance, beginning of period (in shares)	826,263,000	1,140,215,000
Restricted Stock Units Outstanding, Grants (in shares)	353,891,000	167,343,000
Restricted Stock Units Outstanding, Vested (in shares)	(145,157,000)	(270,959,000)
Restricted Stock Units Outstanding, Forfeited (in shares)	(19,269,000)	(11,727,000)
Restricted Stock Units Outstanding, Balance, end of period (in shares)	1,015,728,000	1,024,872,000
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Balance, beginning of period (USD per share)	$ 23.76	$ 21.96
Weighted Average Grant Date Fair Value, Grants (USD per share)	31.12	34.05
Weighted Average Grant Date Fair Value, Vested (USD per share)	31.67	24.00
Weighted Average Grant Date Fair Value, Forfeited (USD per share)	33.19	24.56
Weighted Average Grant Date Fair Value, Balance, end of period (USD per share)	$ 25.83	$ 23.67

Business Acquisition, Equity Interest Issued or Issuable, Number of Shares Issued To Employees

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Share based compensation arrangement by share based payment award equity instruments other than options vested and nonvested number.

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Share based compensation arrangement by share based payment award equity instruments other than options vested and nonvested weighted average grant date fair value.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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