BUSINESS COMBINATIONS (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended		12 Months Ended
	Apr. 01, 2018	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Business Acquisition [Line Items]
Cash consideration	$ 43
Stock consideration	1,043,424
Warrant consideration	14,460
Options consideration	1,577
Total purchase consideration	1,059,504	$ 117,000
Cash	71,806
Investment securities available-for-sale	900,935
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Held to Maturity Securities	171,423
Other investments	28,763
Loans	2,792,572
Premises and equipment	98,814
Intangible assets	42,887
Other assets	167,829
Assets held for sale	127,775
Total assets acquired	4,402,804
Deposits	3,263,920
Subordinated notes	49,027
FHLB advances	291,887
Other borrowings	205,620
Other liabilities	32,649
Liabilities held for sale	175,840
Total liabilities assumed	4,018,943	$ (5)	$ (5)	$ 4,007,743
Net identifiable assets	383,861
Goodwill	$ 675,643		$ (524)	$ 678,941	$ 676,167