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Business Combinations - Narrative (Details) |  |  | 12 Months Ended
--- | --- | --- | ---
Nov. 30, 2020 USD ($) | Nov. 30, 2019 USD ($) banking_location $ / shares shares | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Business Acquisition [Line Items] |  |  |  |  |
Goodwill |  |  | $ 373,424,000 | $ 373,424,000 |
Adjustments, loans |  |  | 6,700,000 | 8,600,000 |
Merger related expenses |  |  | 0 | 2,342,000 | $ 11,350,000
Professional services and legal |  |  | $ 6,368,000 | 6,394,000 | 4,244,000
DNB |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Number of banking locations | banking_location |  | 14 |  |  |
Shares of S&T offered for each share of DNB (in shares) | shares |  | 1.22 |  |  |
Fair value of total consideration | $ 200,991,000 | $ 200,991,000 |  |  |
Cash | 360,000 | $ 360,000 |  |  |
S&T common shares issued (in shares) | shares |  | 5,318,964 |  |  |
S&T common shares issued, fair value (in USD per share) | $ / shares |  | $ 37.72 |  |  |
Goodwill | 85,978,000 | $ 84,175,000 |  | 86,000,000 |
Preliminary estimates adjustments | 1,803,000 |  |  |  |
Adjustments, loans | 2,377,000 | 8,143,000 |  |  |
Adjustments, borrowings | 257,000 | 276,000 |  |  |
Adjustment, other liabilities | 122,000 | 3,184,000 |  |  |
Adjustments, other assets | 116,000 | 4,278,000 |  |  |
Adjustments, deferred income taxes | 311,000 | (3,298,000) |  |  |
Carryover of allowance for credit losses | 0 | 0 |  |  |
Fair value of loans acquired | $ 906,607,000 | 908,984,000 |  |  |
Discount on loans acquired |  | $ 10,500,000 |  |  |
Direct costs related to merger |  |  |  | 13,700,000 |
Merger related expenses |  |  |  | 2,300,000 | 11,400,000
Professional services and legal |  |  |  | 200,000 | 2,800,000
Severance payments |  |  |  | 1,400,000 | 3,400,000
Data processing, contract termination and conversion cost expenses |  |  |  | 400,000 | 4,700,000
Other expenses |  |  |  | $ 300,000 | $ 500,000

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