ACQUISITIONS (Details Textual) (USD $)	0 Months Ended	3 Months Ended								12 Months Ended
	Nov. 09, 2012	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Business Acquisition [Line Items]
Merger and acquisition expenses		$ 5,474,000	$ 595,000	$ 672,000						$ 6,741,000
Proceeds from sale of loans acquired in acquisition	42,200,000
Pay down of Federal Home Loan Bank Advances	(24,991,000)									(24,991,000)	(67,144,000)	(50,000,000)
Finite-lived intangible asset acquired, useful life										9 years 10 months 24 days
Business Combination, Pro Forma Information [Abstract]
Acquisition related costs net of tax, excluded from pro forma results										4,500,000
Acquisition related costs per share, diluted, excluded from pro forma results (in dollars per share)										$ 0.20
Core deposit intangibles [Member]
Business Acquisition [Line Items]
Finite-lived intangible asset acquired, useful life										9 years
Central Bankcorp, Inc. [Member]
Business Acquisition [Line Items]
Cost of acquired entity, cash paid per share option (in dollars per share)	$ 32.00
Number of shares of company stock issued for each share of Central common stock (in shares)	1.0533
Value of shares of company stock issued for each share of acquiree stock (in dollars per share)	$ 29.95
Company's closing price per share (in dollars per share)	$ 28.44
Business transaction value	52,000,000
Cost of acquired entity, percentage cash	40.00%
Cost of acquired entity, percentage stock consideration	60.00%
Cost of acquired entity, cash paid	21,600,000
Cost of acquired entity, stock consideration	30,400,000
Increase in acquirer outstanding shares	1,068,514
Merger and acquisition expenses										6,700,000
Loans acquired	450,671,000
Interest income attributable to acquired loans										$ 3,100,000