ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 2,647,088	$ 2,469,582
Reclassification for gains included in net income, net of tax	0	0
Current year changes, net of tax	(7,415)	21,556
Balance at end of period	2,757,596	2,437,150
Unrealized Gain (Loss) on Derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	0	(147)
Reclassification for gains included in net income, net of tax	0	0
Current year changes, net of tax	0	(97)
Balance at end of period	0	(244)
Unrealized Gain (Loss) on Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	33,505	18,142
Reclassification for gains included in net income, net of tax	0	0
Current year changes, net of tax	(7,415)	21,653
Balance at end of period	26,090	39,795
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	33,505	17,995
Balance at end of period	$ 26,090	$ 39,551