Regulatory Matters - Summary of Risk-Based Capital Amounts and Ratios (Details) $ in Thousands	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
S&T
Leverage Ratio, Amount
Actual	$ 1,112,126	$ 1,034,828
Minimum Regulatory Capital Requirements	371,211	369,297
To be Well Capitalized Under Prompt Corrective Action Provisions	$ 464,014	$ 461,621
Leverage Ratio, Ratio
Actual	0.1198	0.1121
Minimum Regulatory Capital Requirements	0.0400	0.0400
To be Well Capitalized Under Prompt Corrective Action Provisions	0.0500	0.0500
Common Equity Tier 1 ratio, Amount
Actual	$ 1,088,126	$ 1,010,828
Minimum Regulatory Capital Requirements	335,888	340,159
To be Well Capitalized Under Prompt Corrective Action Provisions	$ 485,172	$ 491,341
Common Equity Tier 1 ratio, Ratio
Actual	0.1458	0.1337
Minimum Regulatory Capital Requirements	0.0450	0.0450
To be Well Capitalized Under Prompt Corrective Action Provisions	0.0650	0.0650
Tier 1 Capital (to Risk-Weighted Assets), Amount
Actual	$ 1,112,126	$ 1,034,828
Minimum Regulatory Capital Requirements	447,851	453,545
To be Well Capitalized Under Prompt Corrective Action Provisions	$ 597,134	$ 604,727
Tier 1 Capital (to Risk-Weighted Assets), Ratio
Actual	0.1490	0.1369
Minimum Regulatory Capital Requirements	0.0600	0.0600
To be Well Capitalized Under Prompt Corrective Action Provisions	0.0800	0.0800
Total Capital (to Risk-Weighted Assets), Amount
Actual	$ 1,230,497	$ 1,154,376
Minimum Regulatory Capital Requirements	597,134	604,727
To be Well Capitalized Under Prompt Corrective Action Provisions	$ 746,418	$ 755,909
Total Capital (to Risk-Weighted Assets), Ratio
Actual	0.1649	0.1527
Minimum Regulatory Capital Requirements	0.0800	0.0800
To be Well Capitalized Under Prompt Corrective Action Provisions	0.1000	0.1000
S&T Bank
Leverage Ratio, Amount
Actual	$ 1,060,010	$ 995,824
Minimum Regulatory Capital Requirements	371,002	369,133
To be Well Capitalized Under Prompt Corrective Action Provisions	$ 463,752	$ 461,416
Leverage Ratio, Ratio
Actual	0.1143	0.1079
Minimum Regulatory Capital Requirements	0.0400	0.0400
To be Well Capitalized Under Prompt Corrective Action Provisions	0.0500	0.0500
Common Equity Tier 1 ratio, Amount
Actual	$ 1,060,010	$ 995,824
Minimum Regulatory Capital Requirements	335,722	339,954
To be Well Capitalized Under Prompt Corrective Action Provisions	$ 484,932	$ 491,045
Common Equity Tier 1 ratio, Ratio
Actual	0.1421	0.1318
Minimum Regulatory Capital Requirements	0.0450	0.0450
To be Well Capitalized Under Prompt Corrective Action Provisions	0.0650	0.0650
Tier 1 Capital (to Risk-Weighted Assets), Amount
Actual	$ 1,060,010	$ 995,824
Minimum Regulatory Capital Requirements	447,629	453,272
To be Well Capitalized Under Prompt Corrective Action Provisions	$ 596,839	$ 604,362
Tier 1 Capital (to Risk-Weighted Assets), Ratio
Actual	0.1421	0.1318
Minimum Regulatory Capital Requirements	0.0600	0.0600
To be Well Capitalized Under Prompt Corrective Action Provisions	0.0800	0.0800
Total Capital (to Risk-Weighted Assets), Amount
Actual	$ 1,178,335	$ 1,115,315
Minimum Regulatory Capital Requirements	596,839	604,362
To be Well Capitalized Under Prompt Corrective Action Provisions	$ 746,049	$ 755,453
Total Capital (to Risk-Weighted Assets), Ratio
Actual	0.1579	0.1476
Minimum Regulatory Capital Requirements	0.0800	0.0800
To be Well Capitalized Under Prompt Corrective Action Provisions	0.1000	0.1000

Banking Regulation, Common Equity Tier One Risk-Based Capital Ratio

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Banking Regulation, Total Capital, Ratio

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

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-Topic 942
-SubTopic 505
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-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

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