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Sale of a Majority Interest of Insurance Business (Details) - USD ($) $ in Thousands |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Jan. 01, 2018 | Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Gain on sale of a majority interest of insurance business |  | $ 0 | $ 0 | $ 1,873 | $ 0
New Partnership |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Equity method investment, ownership percentage | 30.00% |  |  |  |
Subsidiaries | S&T Evergreen Insurance LLC |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |
Percentage of ownership in subsidiary sold | 70.00% |  |  |  |
Gain on sale of a majority interest of insurance business | $ 1,900 |  |  |  |

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