INVESTMENT SECURITIES - Composition, Repricing and Yield Information of Investment Securities Portfolio (Details) $ in Thousands	Jun. 30, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 709,698
Securities available-for-sale, one year or less, weighted average yield (percent)	1.64%
Securities available-for-sale, more than one year through five years, fair value	$ 161,468
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	4.62%
Securities available-for-sale, more than five years through ten years, fair value	$ 107,006
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	2.41%
Securities available-for-sale, more than ten years, fair value	$ 374,982
Securities available-for-sale, more than ten years, weighted average yield (percent)	2.12%
Securities available-for-sale, fair value	$ 1,353,154
Weighted-Average Yield	2.17%
SBA loan pool securities
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 16,223
Securities available-for-sale, one year or less, weighted average yield (percent)	1.53%
Securities available-for-sale, more than one year through five years, fair value	$ 0
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	0.00%
Securities available-for-sale, more than five years through ten years, fair value	$ 0
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	0.00%
Securities available-for-sale, more than ten years, fair value	$ 0
Securities available-for-sale, more than ten years, weighted average yield (percent)	0.00%
Securities available-for-sale, fair value	$ 16,223
Weighted-Average Yield	1.53%
U.S. government agency and U.S. government sponsored enterprise residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 0
Securities available-for-sale, one year or less, weighted average yield (percent)	0.00%
Securities available-for-sale, more than one year through five years, fair value	$ 0
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	0.00%
Securities available-for-sale, more than five years through ten years, fair value	$ 29,694
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	2.20%
Securities available-for-sale, more than ten years, fair value	$ 167,991
Securities available-for-sale, more than ten years, weighted average yield (percent)	2.15%
Securities available-for-sale, fair value	$ 197,685
Weighted-Average Yield	2.15%
U.S. government agency and U.S. government sponsored enterprise collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 109,168
Securities available-for-sale, one year or less, weighted average yield (percent)	0.64%
Securities available-for-sale, more than one year through five years, fair value	$ 11,360
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	1.98%
Securities available-for-sale, more than five years through ten years, fair value	$ 43,331
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	1.34%
Securities available-for-sale, more than ten years, fair value	$ 101,325
Securities available-for-sale, more than ten years, weighted average yield (percent)	1.80%
Securities available-for-sale, fair value	$ 265,184
Weighted-Average Yield	1.25%
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 0
Securities available-for-sale, one year or less, weighted average yield (percent)	0.00%
Securities available-for-sale, more than one year through five years, fair value	$ 0
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	0.00%
Securities available-for-sale, more than five years through ten years, fair value	$ 15,469
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	2.62%
Securities available-for-sale, more than ten years, fair value	$ 105,511
Securities available-for-sale, more than ten years, weighted average yield (percent)	2.38%
Securities available-for-sale, fair value	$ 120,980
Weighted-Average Yield	2.41%
Non-agency residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 0
Securities available-for-sale, one year or less, weighted average yield (percent)	0.00%
Securities available-for-sale, more than one year through five years, fair value	$ 0
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	0.00%
Securities available-for-sale, more than five years through ten years, fair value	$ 0
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	0.00%
Securities available-for-sale, more than ten years, fair value	$ 155
Securities available-for-sale, more than ten years, weighted average yield (percent)	6.35%
Securities available-for-sale, fair value	$ 155
Weighted-Average Yield	6.35%
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 584,307
Securities available-for-sale, one year or less, weighted average yield (percent)	1.82%
Securities available-for-sale, more than one year through five years, fair value	$ 0
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	0.00%
Securities available-for-sale, more than five years through ten years, fair value	$ 0
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	0.00%
Securities available-for-sale, more than ten years, fair value	$ 0
Securities available-for-sale, more than ten years, weighted average yield (percent)	0.00%
Securities available-for-sale, fair value	$ 584,307
Weighted-Average Yield	1.82%
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 0
Securities available-for-sale, one year or less, weighted average yield (percent)	0.00%
Securities available-for-sale, more than one year through five years, fair value	$ 150,108
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	4.82%
Securities available-for-sale, more than five years through ten years, fair value	$ 18,512
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	5.73%
Securities available-for-sale, more than ten years, fair value	$ 0
Securities available-for-sale, more than ten years, weighted average yield (percent)	0.00%
Securities available-for-sale, fair value	$ 168,620
Weighted-Average Yield	4.91%

Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Weighted average yield of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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