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v3.20.1

Business Combinations - Additional Information (Details) |  |  |  | 3 Months Ended | 4 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Nov. 30, 2019 USD ($) banking_location $ / shares shares | Mar. 31, 2020 USD ($) | Mar. 31, 2019 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |
Goodwill | $ 374,270,000 | $ 371,621,000 |  |  | $ 374,270,000 |  | $ 374,270,000 | $ 371,621,000
Adjustments, Loans | 10,900,000 | $ 12,300,000 |  |  |  |  |  |
Merger related expenses |  |  |  |  | 2,342,000 | $ 0 |  |
Professional services and legal |  |  |  |  | 1,048,000 | $ 1,184,000 |  |
DNB |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |
Number of banking locations | banking_location |  |  | 14 |  |  |  |  |
Shares of S&T offered for each share of DNB (shares) | shares |  |  | 1.22 |  |  |  |  |
Fair value of total consideration |  |  | $ 200,991,000 |  |  |  |  |
Cash |  |  | $ 360,000 |  |  |  |  |
S&T common shares issued (shares) | shares |  |  | 5,318,964 |  |  |  |  |
S&T common shares issued, fair value (in dollars per share) | $ / shares |  |  | $ 37.72 |  |  |  |  |
Goodwill | 85,983,000 |  | $ 84,175,000 |  | 85,983,000 |  | 85,983,000 |
Preliminary estimates adjustments |  |  |  |  |  |  | 1,808,000 |
Adjustments, Loans |  |  | 8,143,000 | [1] | (2,500,000) |  | 2,496,000 |
Adjustments, Borrowings |  |  | 276,000 | [1] |  |  | 257,000 |
Adjustments, Deferred income taxes |  |  | (3,298,000) | [1] |  |  | 311,000 |
Carryover of allowance for credit losses | 0 |  | 0 |  | 0 |  | 0 |
Fair value of loans acquired | 906,488,000 |  | 908,984,000 |  | 906,488,000 |  | 906,488,000 |
Discount on loans acquired |  |  | $ 10,500,000 |  |  |  |  |
Direct costs related to merger | $ 13,700,000 |  |  |  | 13,700,000 |  | $ 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
[1] | Management is continuing to evaluate the purchase accounting fair value adjustments related to loans, including loan classification, deferred and current income taxes until the final valuations are complete and final tax returns are filed. Any changes in preliminary estimates will be adjusted in goodwill in subsequent periods, but not extending beyond one year from the date of acquisition.

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