ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 2,837,004	$ 2,460,130	$ 2,647,088	$ 2,469,582
Reclassification for gains included in net income, net of tax	0	0	0	0
Current year changes, net of tax	(3,139)	(2,361)	(11,620)	19,257
Balance at end of period	2,900,770	2,564,683	2,900,770	2,564,683
Unrealized Gain (Loss) on Derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	0	(133)	0	(147)
Reclassification for gains included in net income, net of tax	0	0	0	0
Current year changes, net of tax	0	133	0	147
Balance at end of period	0	0	0	0
Unrealized Gain (Loss) on Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	25,024	39,746	33,505	18,142
Reclassification for gains included in net income, net of tax	0	0	0	0
Current year changes, net of tax	(3,139)	(2,494)	(11,620)	19,110
Balance at end of period	21,885	37,252	21,885	37,252
Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	25,024	39,613	33,505	17,995
Balance at end of period	$ 21,885	$ 37,252	$ 21,885	$ 37,252