Business acquisition number of share offered for each share of acquiree entity.

No definition available.

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Period Type:	duration

- Definition

Business acquisition shareholders entitled to receive cash for each share.

+ References

No definition available.

+ Details

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- Definition

Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Fair Value, Per Share

+ References

No definition available.

+ Details

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- Definition

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Allowance for Loan Losses

+ References

No definition available.

+ Details

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- Definition

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loan Discount

+ References

No definition available.

+ Details

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- Definition

Data processing contract termination and conversion cost expenses.

+ References

No definition available.

+ Details

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- Definition

Legal and professional expenses.

+ References

No definition available.

+ Details

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- Definition

Number of shares of equity interests issued or issuable to acquire entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)(4)

-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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Balance Type:	na
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- Details

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Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the fair value of the receivables acquired, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472

+ Details

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Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 30

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

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-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

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- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

+ Details

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- Definition

Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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-Name Accounting Standards Codification

-Topic 420

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-Section 50

-Paragraph 1

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

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-Topic 420

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-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.P.3)

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

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-Paragraph 1

-Subparagraph (a)(10)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Details

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Business Combinations - Additional Information (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 04, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 290,617,000us-gaap_Goodwill			$ 175,820,000us-gaap_Goodwill
Carryover of allowance for loan losses	0
Merger related expenses	2,301,000	0
Integrity Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired			100.00%
Business acquisition, cash per share offered in exchange of share			$ 52.50
Shares of S&T offered for each share of Integrity (shares)			2.0627
Fair value of total consideration			171,979,000
Cash			29,510,000
S&T common shares issued (shares)			4,933,115
S&T common shares issued, fair value (in USD per share)			$ 28.88
Goodwill			114,797,000
Carryover of allowance for loan losses			0
Fair value of loans acquired			788,687,000
Discount on loans acquired			14,800,000
Merger related expenses	2,300,000
Data processing, contract termination and conversion cost expenses	900,000
Severance payments	300,000
Legal And professional expenses	1,100,000
Commercial Real Estate [Member] \| Integrity Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Fair value of loans acquired			481,400,000
Commercial and Industrial [Member] \| Integrity Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Fair value of loans acquired			193,900,000
Commercial Construction [Member] \| Integrity Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Fair value of loans acquired			44,800,000
Residential Mortgage [Member] \| Integrity Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Fair value of loans acquired			32,700,000
Home Equity [Member] \| Integrity Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Fair value of loans acquired			28,800,000
Installment and Other Consumer [Member] \| Integrity Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Fair value of loans acquired			5,600,000
Consumer Construction [Member] \| Integrity Bancshares, Inc. [Member]
Business Acquisition [Line Items]
Fair value of loans acquired			$ 1,500,000