LOANS, Loan Summary (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Loans receivable, net [Abstract]
Contract term of consumer mortgages, minimum	15 years
Contract term of consumer mortgages, maximum	30 years
Contract term of home equity loans, maximum	15 years
Gross loans, including deferred origination costs	$ 3,935,998,000		$ 3,865,576,000
Allowance for loan losses	(43,473,000)	(42,913,000)	(42,888,000)	(41,828,000)	(41,809,000)	(42,213,000)
Net loans	3,892,525,000		3,822,688,000
Credit impaired acquired loans, outstanding balance	20,200,000		22,400,000
Accretable discount related to acquired loans [Roll forward]
Beginning Balance	1,770,000
Accretion recognized, year-to-date	(538,000)
Net reclassification to accretable from nonaccretable	29,000
Ending Balance	1,261,000
Consumer Mortgage [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	1,527,341,000		1,448,415,000
Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	1,225,671,000		1,233,944,000
Consumer Indirect [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	663,924,000		647,518,000
Consumer Direct [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	171,727,000		171,474,000
Home Equity [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 347,335,000		$ 364,225,000