ACQUISITIONS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	May 12, 2017	Dec. 31, 2016	Nov. 10, 2016	Dec. 31, 2015
Assets
Goodwill	$ 231,806		$ 221,526		$ 201,083
Island Bancorp, Inc. [Member]
Assets
Cash		$ 11,137
Loans		155,551
Premises and equipment		5,828
Goodwill		10,280
Core deposit intangible		2,964
Other assets		4,629
Total assets acquired		190,389
Liabilities
Deposits		159,580
Borrowings		2,475
Other liabilities		18
Total liabilities assumed		162,073
Purchase price		$ 28,316
New England Bancorp, Inc. [Member]
Assets
Cash				$ 9,679
Loans				225,731
Premises and equipment				201
Goodwill				20,443
Core deposit intangible				670
Other assets				19,197
Total assets acquired				275,921
Liabilities
Deposits				175,686
Borrowings				51,150
Other liabilities				7,344
Total liabilities assumed				234,180
Purchase price				$ 41,741