INVESTMENT SECURITIES - Summary of Amortized Cost and Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 1,198,091	$ 929,449
Gross Unrealized Gains	13,924	151
Gross Unrealized Losses	(35,986)	(17,020)
Securities available-for-sale, at fair value	1,176,029	912,580
U.S. government agency and U.S. government sponsored enterprise residential mortgage-backed securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	100,128	37,613
Gross Unrealized Gains	5,427	0
Gross Unrealized Losses	0	(1,157)
Securities available-for-sale, at fair value	105,555	36,456
U.S. government agency and U.S. government sponsored enterprise collateralized mortgage obligations
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	199,262	91,543
Gross Unrealized Gains	1,906	16
Gross Unrealized Losses	(32)	(260)
Securities available-for-sale, at fair value	201,136	91,299
Municipal securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	52,973	52,997
Gross Unrealized Gains	4,201	51
Gross Unrealized Losses	0	(359)
Securities available-for-sale, at fair value	57,174	52,689
Non-agency residential mortgage-backed securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	161	191
Gross Unrealized Gains	3	5
Gross Unrealized Losses	0	0
Securities available-for-sale, at fair value	164	196
Collateralized loan obligations
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	703,605	733,605
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(35,252)	(15,244)
Securities available-for-sale, at fair value	668,353	718,361
Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	141,962	13,500
Gross Unrealized Gains	2,387	79
Gross Unrealized Losses	(702)	0
Securities available-for-sale, at fair value	$ 143,647	$ 13,579

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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