BUSINESS COMBINATIONS - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Mar. 01, 2019	Mar. 31, 2019	Dec. 31, 2018
Liabilities assumed:
Goodwill resulting from acquisition of Beneficial		$ 475,493	$ 166,007
Beneficial
Business Acquisition [Line Items]
Common shares issued (21,816,355)	$ 949,968
Cash paid to Beneficial stock and option holders	228,239
Value of consideration	$ 1,178,207
Number of shares issued (in shares)	21,816,355
Assets acquired:
Cash and due from banks	$ 304,557
Investment securities	616,703
Loans and leases, net	3,712,157
Premises and equipment	69,132
Deferred income taxes	19,470
Bank owned life insurance	82,510
Total assets	135,474
Total assets	5,027,522
Liabilities assumed:
Deposits	4,055,716
Other liabilities	103,085
Total liabilities	4,158,801
Net assets acquired:	868,721
Goodwill resulting from acquisition of Beneficial	309,486
Core deposits | Beneficial
Assets acquired:
Core deposit intangible	85,053
Loan servicing rights | Beneficial
Assets acquired:
Core deposit intangible	$ 2,466