ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Summary of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ 2,469,582	$ 1,456,347	$ 804,479
Reclassification for gains included in net income, net of tax	0	(46)	(70)
Current year changes, net of tax	15,510	22,867	(3,084)
Balance at end of period	2,647,088	2,469,582	1,456,347
Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period			(392)
Cumulative Effect, Period of Adoption, Adjusted Balance
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period			(1,672)
Unrealized Gain (Loss) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(147)	351	292
Reclassification for gains included in net income, net of tax	0	0	0
Current year changes, net of tax	147	(498)	112
Balance at end of period	0	(147)	351
Unrealized Gain (Loss) on Derivatives | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period			(53)
Unrealized Gain (Loss) on Derivatives | Cumulative Effect, Period of Adoption, Adjusted Balance
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period			239
Unrealized Gain (Loss) on Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	18,142	(5,177)	(1,572)
Reclassification for gains included in net income, net of tax	0	(46)	(70)
Current year changes, net of tax	15,363	23,365	(3,196)
Balance at end of period	33,505	18,142	(5,177)
Unrealized Gain (Loss) on Securities | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period			(339)
Unrealized Gain (Loss) on Securities | Cumulative Effect, Period of Adoption, Adjusted Balance
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period			(1,911)
Accumulated Other Comprehensive Income (Loss), Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	17,995	(4,826)	(1,280)
Balance at end of period	$ 33,505	$ 17,995	$ (4,826)