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Subsequent Event (Details) - USD ($) $ in Millions |  | 2 Months Ended |
--- | --- | --- | ---
Jan. 01, 2018 | Feb. 28, 2018 | Dec. 31, 2017
Subsequent Event [Line Items] |  |  |
Percentage of equity owned |  |  | 100.00%
Subsequent Event | Subsidiary | S&T Evergreen Insurance, LLC |  |  |
Subsequent Event [Line Items] |  |  |
Proceeds from sale of majority interest in subsidiary | $ 5.0 |  |
Recognized gain on sale of subsidiary |  | $ 1.0 |
Subsequent Event | S&T Evergreen Insurance, LLC |  |  |
Subsequent Event [Line Items] |  |  |
Percentage of equity owned | 30.00% |  |

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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571 + Details
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- Definition Amount of gain (loss) on sale or disposal of equity in securities of subsidiaries. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (13)(g) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition The cash inflow associated with the deconsolidation of a previously consolidated subsidiary or the sale of investment in consolidated subsidiaries (generally greater than 50 percent). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585 + Details
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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
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