ACQUISITIONS (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	May 12, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Acquisition Related Costs		$ 0	$ 151	$ 3,393	$ 691
Island Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Equity Interest Issued or Issuable Shareholders Option To Receive, Cash Per Share	$ 500
Business Combination, Cost of Acquired Entity, Purchase Price	$ 28,300
Number of shares of company stock issued for each share of Central common stock (in shares)	9.525
Value of shares of company stock issued for each share of acquiree stock (in dollars per share)	$ 605.31
Share Price	$ 63.55
Increase in acquirer outstanding shares	369,286
Payments to Acquire Businesses, Gross	$ 4,800
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	$ 23,500
Business Acquisition, Cost of Acquired Entity, Percentage Cash Paid	20.00%
Business Acquisition, Cost of Acquired Entity, Percentage Stock Consideration	80.00%
Acquisition Related Costs				3,200
Combination of INDB and Island Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Acquisition Related Costs		$ 0	$ 0	$ 2,600