ACQUISITIONS (Details) (USD $)	3 Months Ended		12 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Feb. 24, 2015
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Goodwill	$ 375,174,000	$ 375,174,000	$ 375,174,000
Merger and acquisition integration-related expenses	400,000	100,000
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life of core deposit intangible and other intangible	8 years
Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life of core deposit intangible and other intangible	8 years
EBS-RMSCO, Inc. [Member]
Consideration paid/(received) [Abstract]
Cash/Total net consideration paid/(received)			924,000
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Other assets/( liabilities), net			163,000
Other intangibles			578,000
Total identifiable assets/(liabilities), net			741,000
Goodwill			183,000
Oneida Financial Corp [Member]
Consideration paid/(received) [Abstract]
Cash/Total net consideration paid/(received)				142,000,000
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Number of new branch locations included in acquisition or purchase agreement				12
Assets acquired				800,000,000
Loans acquired				370,000,000
Deposits acquired				$ 690,000,000