ACQUISITIONS (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Apr. 01, 2019	Dec. 31, 2018	Nov. 16, 2018	Dec. 31, 2017
Assets
Goodwill	$ 506,206		$ 256,105		$ 231,806
Blue Hills Bancorp, Inc. [Member]
Assets
Cash		$ 56,331
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Investments		196,937
Loans		2,073,714
Premises and equipment		24,253
Goodwill		250,101
Core deposit intangible		19,870
Other assets		146,192
Total assets acquired		2,767,398
Liabilities
Deposits		1,930,436
Borrowings		124,817
Other liabilities		50,857
Total liabilities assumed		2,106,110
Purchase price		$ 661,288
MNB Bancorp [Member]
Assets
Cash				$ 6,743
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Investments				25,358
Loans				293,498
Premises and equipment				1,904
Goodwill				24,299
Core deposit intangible				8,588
Other assets				8,639
Total assets acquired				369,029
Liabilities
Deposits				278,204
Borrowings				33,093
Other liabilities				1,609
Total liabilities assumed				312,906
Purchase price				$ 56,123