STOCKHOLDERS' EQUITY - Changes to Accumulate Other Comprehensive Income by Components (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Gain (loss) on securities available-for-sale
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	$ (11,542)	$ 5,227	$ (9,702)	$ 5,227	$ (9,042)
Unrealized gain (loss) arising during the period	(10,796)		10,923	(30,478)	13,149
Reclassification adjustment from other comprehensive income	(278)		(1,099)	(5,519)	(4,455)
Tax effect of current period changes	3,246		(13,231)	10,904	(12,761)
Total changes, net of taxes	(7,828)		18,583	(25,093)	17,923
Reclassification of stranded tax effects to retained earnings	0		0	496	0
Balance at end of period	(19,370)	$ (11,542)	8,881	(19,370)	8,881
Unrealized gain arising from the reclassification of securities held-to-maturity to securities available-for-sale
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Unrealized gain (loss) arising during the period	$ 0		$ 21,990	$ 0	$ 21,990

Tax Cuts And Jobs Act Of 2017, Reclassification From AOCI To Retained Earnings, Tax Effect

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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