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Loans and Allowance for Credit Losses - Additional Information (Details)		3 Months Ended		9 Months Ended
	Apr. 01, 2024 USD ($)	Sep. 30, 2024 USD ($) portfolio segment	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) portfolio segment	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan participations		$ 3,400,000,000		$ 3,400,000,000
Loan participations sold		1,500,000,000		1,500,000,000
Loan participations retained		$ 1,900,000,000		$ 1,900,000,000
Number of loan portfolios | portfolio		4		4
Number of loan segments | segment		7		7
Allowance for credit losses at acquisition	$ 26,725,000
Provision for credit losses		$ 28,497,000	$ 19,068,000	$ 83,602,000	$ 47,292,000
Loan placed on nonaccrual when past due, number of days				90 days
Payment defaults		3,900,000	$ 0	$ 25,300,000	$ 0
Unfunded commitments on TDRs		0		0		$ 0
CapStar Financial Holdings, Inc.
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for credit losses at acquisition	$ 26,700,000
Provision for credit losses				15,300,000
Accrued interest receivable on loans		$ 174,800,000		$ 174,800,000		$ 169,800,000
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Percentage of risk-based capital		241.00%		241.00%
Regulatory guideline limit		300.00%		300.00%

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Commercial real estate loans as a percentage of risk-based capital.

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Amount, before allowance for credit loss, of accrued interest on financing receivable.

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