Spirit of Texas Bancshares, Inc. Annual report pursuant to Section 13 and 15(d)

Investment Securities - Additional Information (Details)

v3.22.0.1

Investment Securities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) Security	Dec. 31, 2020 USD ($) Security	Dec. 31, 2019 USD ($) Security
Marketable Securities [Line Items]
Available for sale securities pledged	$ 281,800,000	$ 91,500,000
Debt Securities, Available-for-sale, Restriction Type [Extensible List]	us-gaap:CollateralPledgedMember	us-gaap:CollateralPledgedMember
Available for sale, securities number of positions \| Security	105
Available for sale, securities in unrealized loss positions, number of positions \| Security	70
Available for sale securities, gross realized gain (loss), excluding other than temporary impairments	$ 0
Number of securities sold \| Security	5	46	216
Equity investments, at fair value	$ 23,665,000	$ 24,000,000
Fair value changes		0
Taxable interest and dividends on investment securities	5,700,000	2,100,000	$ 4,600,000
Tax-exempt interest on investment securities	627,000	$ 193,000	$ 541,000
Other Noninterest Income
Marketable Securities [Line Items]
Fair value changes	669,000
Dividend Income
Marketable Securities [Line Items]
Fair value changes	$ 334,000

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Number of securities sold.

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Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), excluding other-than-temporary impairment (OTTI).

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Indicates type of restriction on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of operating dividend income on securities subject to state, federal and other income tax.

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Fair value portion of investments accounted under the equity method.

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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities exempt from state, federal and other income tax.

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