Represents the number of banking centers operated by the acquiree.

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Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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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.

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Amount of increase (decrease) of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of income tax expense (benefit) from continuing operations attributable to an adjustment of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity.

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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Acquisitions (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended
	Mar. 08, 2013 Branch	Dec. 31, 2014	Dec. 31, 2013
Alliance Financial Corporation [Member]
Business Acquisition [Line Items]
Date of acquisition		Mar. 08, 2013
Total consideration paid	$ 226
Number of banking centers operated by acquiree	26
Other goodwill adjustments [Abstract]
Deferred tax adjustments		(1.0)
Valuation adjustments		(0.4)
Decrease in goodwill		(1.4)
Hampshire First Bank [Member]
Other goodwill adjustments [Abstract]
Decrease in goodwill			(1.0)
Acquisition of Financial Services Company [Member]
Other goodwill adjustments [Abstract]
Goodwill adjustment related to business acquisition			$ 0.1