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Right-Of-Use Assets and Lease Liabilities - Narrative (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 USD ($) director lease | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Lessee, Lease, Description [Line Items] |  |  |
Number of lease contracts | lease | 51 |  |
Number of operating lease agreements | lease | 48 |  |
Number of financing leases | lease | 3 |  |
Operating lease expense | $ 5,711 | $ 4,221 | $ 3,850
Number of operating leases considered abandoned | lease | 2 |  |
Reduction of right-of-use asset value | $ 500 |  |
Right-of-use asset value after reduction | 0 |  |
Reduction of operating lease liability | 200 |  |
Expense recognized from lease abandonment | $ 300 |  |
Related party, lease with S&T Director |  |  |
Lessee, Lease, Description [Line Items] |  |  |
Number of directors | director | 1 |  |
Operating lease expense | $ 200 | 200 | $ 200
DNB |  |  |
Lessee, Lease, Description [Line Items] |  |  |
ROU asset acquired from DNB merger |  | $ 10,900 |

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- Definition Amount of operating lease expense. Excludes sublease income. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918638-209977 + Details
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