ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 2,469,582	$ 1,456,347
Reclassification for gains included in net income, net of tax	0	(46)
Current year changes, net of tax	21,556	3,694
Balance at end of period	2,437,150	1,495,584
Unrealized Gain (Loss) on Derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(147)	351
Reclassification for gains included in net income, net of tax	0	0
Current year changes, net of tax	(97)	(173)
Balance at end of period	(244)	178
Unrealized Gain (Loss) on Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	18,142	(5,177)
Reclassification for gains included in net income, net of tax	0	(46)
Current year changes, net of tax	21,653	3,867
Balance at end of period	39,795	(1,356)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	17,995	(4,826)
Balance at end of period	$ 39,551	$ (1,178)