INCOME TAXES (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income taxes
Net deferred tax assets related to acquisitions	$ 57,729,000	$ 40,744,000	$ 18,674,000
Net increase in valuation allowance	609,000
Net operating loss carryforwards	20,700,000
Alternative minimum tax credit carryforwards	2,900,000
Unrecognized income tax benefits
Unrecognized income tax benefits at the beginning of the period	774,000
Increase in gross amounts of tax positions related to prior years	173,000	774,000
Decrease in gross amounts of tax positions related to prior years	(140,000)
Increase in gross amounts of tax positions related to current years	50,000
Decrease due to settlement with taxing authority	(240,000)
Decrease due to lapse in statute of limitations	(125,000)
Unrecognized income tax benefits at the end of the period	492,000	774,000
General business tax credit carryforwards
Income taxes
Tax credit carryforwards	5,600,000
Capital loss carryforwards
Income taxes
Other tax credit carryforwards	4,900,000
Tax credit in limited partnerships investments
Income taxes
Valuation allowance	2,100,000
Beacon
Income taxes
Increase in net deferred tax assets	19,100,000
CBT
Income taxes
Increase in net deferred tax assets	8,500,000
Greenpark
Income taxes
Increase in net deferred tax assets	437,000
Legacy Bancorp, Inc.
Income taxes
Net deferred tax assets related to acquisitions		19,800,000
Rome Bancorp, Inc.
Income taxes
Net deferred tax assets related to acquisitions		$ 2,800,000