ACQUISITIONS (Details) (USD $)	3 Months Ended	6 Months Ended			12 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2012 Core Deposits [Member]	Dec. 31, 2012 HSBC and First Niagara [Member]	Dec. 31, 2012 HSBC and First Niagara [Member] Acquired Impaired Loans [Member]	Dec. 31, 2012 HSBC and First Niagara [Member] Acquired Non-Impaired Loans [Member]	Jul. 20, 2012 HSBC Branch Agreement [Member] Branch	Sep. 07, 2012 First Niagara Branch Agreement [Member] Branch
Business Acquisition [Line Items]
Number of new branch locations included in acquisition or purchase agreement									16	3
Loans acquired									$ 106,000,000	$ 54,000,000
Deposits acquired									697,000,000	101,000,000
Blended deposit premium (in hundredths)									3.40%	3.10%
Total deposit premium paid									24,000,000	3,000,000
Consideration received [Abstract]
Cash/Total net consideration received						(595,462,000)
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents						5,510,000
Loans						160,116,000
Premises and equipment						4,941,000
Accrued interest receivable						588,000
Other assets and liabilities, net						171,000
Core deposit intangibles						6,521,000
Deposits						(797,962,000)
Total identifiable liabilities, net						(620,115,000)
Goodwill	345,050,000	345,050,000	369,703,000	369,703,000		24,653,000
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition						201,745,000	0	201,745,000
Contractual cash flows not expected to be collected						(3,555,000)	0	(3,555,000)
Expected cash flows at acquisition						198,190,000	0	198,190,000
Interest component of expected cash flows						(38,074,000)	0	(38,074,000)
Fair value of acquired loans						160,116,000	0	160,116,000
Merger and acquisition integration related expenses	$ 200,000	$ 400,000
Finite-Lived Intangible Assets [Line Items]
Estimated useful life of core deposit intangible and other intangible					8 years