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Debt Instrument, Offering Price, Percent

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Number Of Issuances Of Trust Securities

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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Other Borrowings and Subordinated Notes and Debentures - Narrative (Details)	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($)	Sep. 30, 2022 USD ($) issuance	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Advances from Federal Home Loan Banks			$ 838,500,000
Mortgage loans and investment securities securing FHLB advances			6,600,000,000
Additional advances from Federal Home Loan Bank			5,400,000,000
FHLB advances outstanding			785,000,000
Early retirement of debt			(365,000)	$ 0	$ 0
Federal Home Loan Bank Owns the Options (FOTO) Advances
Debt Instrument [Line Items]
Advances from Federal Home Loan Banks			$ 835,000,000
Subordinated Debt
Debt Instrument [Line Items]
Face amount of debt	$ 330,000,000
Debt instrument, interest rate	5.00%		5.00%
Offering price, percent	100.00%
Debt issuance costs	$ 3,600,000
Subordinated Debt \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Floating rate (as percent)	2.15%
Subordinated Debt \| Subordinated notes payable, net of premium adjustments, due 7/31/2030, fixed-to-floating rate (fixed rate of 6.00% through 7/30/2025, floating rate of 5.92% above the three month SOFR rate, reset quarterly)
Debt Instrument [Line Items]
Debt instrument, interest rate			6.00%
Long-term debt, gross			$ 37,285,000	$ 0
Subordinated Debt \| Subordinated notes payable, net of premium adjustments, due 7/31/2030, fixed-to-floating rate (fixed rate of 6.00% through 7/30/2025, floating rate of 5.92% above the three month SOFR rate, reset quarterly) \| Spirit of Texas Bancshares, Inc.
Debt Instrument [Line Items]
Debt instrument, interest rate			6.00%
Long-term debt, gross			$ 37,400,000
Subordinated Debt \| Subordinated notes payable, net of premium adjustments, due 7/31/2030, fixed-to-floating rate (fixed rate of 6.00% through 7/30/2025, floating rate of 5.92% above the three month SOFR rate, reset quarterly) \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Floating rate (as percent)			5.92%
Subordinated Debt \| Subordinated notes payable, net of premium adjustments, due 7/31/2030, fixed-to-floating rate (fixed rate of 6.00% through 7/30/2025, floating rate of 5.92% above the three month SOFR rate, reset quarterly) \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Spirit of Texas Bancshares, Inc.
Debt Instrument [Line Items]
Floating rate (as percent)			592.00%
Trust Preferred Securities
Debt Instrument [Line Items]
Face amount of debt		$ 56,200,000
Number of issuances of trust \| issuance		5
Early retirement of debt		$ 365,000