Refers to the number of branches acquired during the period.

No definition available.

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- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill and Intangible Assets (Details) $ in Millions	1 Months Ended		12 Months Ended
	Nov. 30, 2013 Branch	Mar. 31, 2008 Branch	Dec. 31, 2017 USD ($)
Bank of America
Finite-Lived Intangible Assets [Line Items]
Number of branches acquired \| Branch	6
Finite-lived intangible assets			$ 0.3
Bank of America \| Core Deposits
Finite-Lived Intangible Assets [Line Items]
Useful life			7 years
Partners Trust Bank \| Trust Business
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets			$ 1.3
Useful life			15 years
Fort Orange Financial Corp
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets			$ 0.4
Useful life			10 years
M&T Bank branch offices
Finite-Lived Intangible Assets [Line Items]
Number of branches acquired \| Branch		3
MT Branch Offices and Canton Bancorp, Inc. \| Core Deposits
Finite-Lived Intangible Assets [Line Items]
Useful life			7 years 3 months