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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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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Other Borrowings and Subordinated Notes and Debentures - Textual (Details) - USD ($)	1 Months Ended	6 Months Ended
	Mar. 31, 2018	Jun. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
FHLB advances		$ 1,030,000,000.00	$ 1,310,000,000
Mortgage loans and investment securities securing FHLB advances		4,900,000,000
Additional advances from FHLB		$ 3,700,000,000
Federal Home Loan Bank Owns the Options (FOTO) Advances \| Minimum
Debt Instrument [Line Items]
Debt term		10 years
Federal Home Loan Bank Owns the Options (FOTO) Advances \| Maximum
Debt Instrument [Line Items]
Debt term		15 years
Subordinated debt
Debt Instrument [Line Items]
Subordinated debentures	$ 330,000,000
Fixed rate (as percent)	5.00%
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]
Fixed rate (as percent)		6.00%
Long-term debt, gross		$ 37,341,000	$ 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]
Fixed rate (as percent)		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%