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Basis of Presentation (Details)

3 Months Ended

6 Months Ended

Jan. 01, 2018

USD ($)

Jun. 30, 2018

USD ($)

lease

Mar. 31, 2018

USD ($)

Jun. 30, 2017

USD ($)

Jun. 30, 2018

USD ($)

lease

Jun. 30, 2017

USD ($)

Dec. 31, 2017

USD ($)

Schedule of Equity Method Investments [Line Items]

Provisional estimate for reclassification of AOCI to retain earnings for other income tax effects of Tax Act

$ 3,400,000

Gain on sale of a majority interest of insurance business

$ 0

$ 0

$ 1,873,000

$ 0

Unrealized gains on marketable equity securities

$ 230,000

$ 504,000

$ 282,000

$ 1,237,000

Number of operating lease agreements | lease

50

50

ASU No. 2018-02

Schedule of Equity Method Investments [Line Items]

Effect of new accounting pronouncement on Consolidated Financial Statements

$ 0

ASU No. 2018-02 | AOCI

Schedule of Equity Method Investments [Line Items]

Provisional estimate for reclassification of AOCI to retain earnings for other income tax effects of Tax Act

^[1]

$ (3,427,000)

ASU No. 2018-02 | Retained Earnings

Schedule of Equity Method Investments [Line Items]

Provisional estimate for reclassification of AOCI to retain earnings for other income tax effects of Tax Act

^[1]

3,427,000

ASU No. 2017-07

Schedule of Equity Method Investments [Line Items]

Effect of new accounting pronouncement on Consolidated Financial Statements

0

ASU No. 2017-01

Schedule of Equity Method Investments [Line Items]

Effect of new accounting pronouncement on Consolidated Financial Statements

0

ASU No. 2016-16

Schedule of Equity Method Investments [Line Items]

Effect of new accounting pronouncement on Consolidated Financial Statements

0

ASU No. 2016-15

Schedule of Equity Method Investments [Line Items]

Effect of new accounting pronouncement on Consolidated Financial Statements

0

ASU No. 2014-09

Schedule of Equity Method Investments [Line Items]

Effect of new accounting pronouncement on Consolidated Financial Statements

$ 0

ASU No. 2016-01

Schedule of Equity Method Investments [Line Items]

Unrealized gains on marketable equity securities

$ 300,000

ASU No. 2016-01 | AOCI

Schedule of Equity Method Investments [Line Items]

Effect of new accounting pronouncement on Consolidated Financial Statements

(900,000)

(862,000)

^[2]

ASU No. 2016-01 | Retained Earnings

Schedule of Equity Method Investments [Line Items]

Effect of new accounting pronouncement on Consolidated Financial Statements

$ 900,000

$ 862,000

^[2]

New Partnership

Schedule of Equity Method Investments [Line Items]

Equity method investment, ownership percentage

30.00%

Subsidiaries | S&T Evergreen Insurance LLC

Schedule of Equity Method Investments [Line Items]

Percentage of ownership in subsidiary sold

70.00%

Gain on sale of a majority interest of insurance business

$ 1,900,000

[1]	Reclassification due to the adoption of ASU No. 2018-02 - $(3,660) relates to funded status of pension and $233 relates to net unrealized gains on available-for-sale securities.
[2]	Reclassification due to the adoption of ASU No. 2016-01.

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