STOCKHOLDERS' EQUITY - Changes to Accumulated Other Comprehensive (Loss) Income by Components (Detail) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Impairment loss on investment securities	$ 0	$ 0	$ (731)	$ 0	$ (731)
Gain (loss) on securities available-for-sale
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(15,565)		(12,668)	(11,900)	(24,117)
Unrealized gain (loss) arising during the period	23,859		(1,408)	20,677	15,014
Unrealized gain arising from the reclassification of securities held-to-maturity to securities available-for-sale	0		0	0	0
Impairment loss on investment securities	0		731	0	731
Reclassification adjustment from other comprehensive income	0		5,063	(2,011)	4,855
Tax effect of current period changes	(7,028)		(1,289)	(5,500)	(6,054)
Total changes, net of taxes	16,831		3,097	13,166	14,546
Balance at end of period	$ 1,266	$ (15,565)	$ (9,571)	$ 1,266	$ (9,571)