INVESTMENT SECURITIES - Composition, Repricing and Yield Information of Investment Securities Portfolio (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 741,736
Securities available-for-sale, one year or less, weighted average yield (percent)	3.22%
Securities available-for-sale, more than one year through five years, fair value	$ 39,267
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	3.32%
Securities available-for-sale, more than five years through ten years, fair value	$ 59,851
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	2.90%
Securities available-for-sale, more than ten years, fair value	$ 128,573
Securities available-for-sale, more than ten years, weighted average yield (percent)	2.55%
Securities available-for-sale, fair value	$ 969,427
Securities available-for-sale, weighted average yield (percent)	3.14%
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	$ 29,993
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	$ 74,028
Securities available-for-sale, more than ten years, weighted average yield (percent)	2.36%
Securities available-for-sale, fair value	$ 104,021
Securities available-for-sale, weighted average yield (percent)	2.32%
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	$ 118,165
Securities available-for-sale, one year or less, weighted average yield (percent)	2.09%
Securities available-for-sale, more than one year through five years, fair value	$ 11,060
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	2.34%
Securities available-for-sale, more than five years through ten years, fair value	$ 10,194
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	2.43%
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	$ 139,419
Securities available-for-sale, weighted average yield (percent)	2.14%
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	$ 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	$ 54,385
Securities available-for-sale, more than ten years, weighted average yield (percent)	2.79%
Securities available-for-sale, fair value	$ 54,385
Securities available-for-sale, weighted average yield (percent)	2.79%
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	$ 160
Securities available-for-sale, more than ten years, weighted average yield (percent)	5.46%
Securities available-for-sale, fair value	$ 160
Securities available-for-sale, weighted average yield (percent)	5.46%
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, one year or less, fair value	$ 623,571
Securities available-for-sale, one year or less, weighted average yield (percent)	3.43%
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	$ 623,571
Securities available-for-sale, weighted average yield (percent)	3.43%
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	$ 28,207
Securities available-for-sale, more than one year through five years, weighted average yield (percent)	3.70%
Securities available-for-sale, more than five years through ten years, fair value	$ 19,664
Securities available-for-sale, more than five years through ten years, weighted average yield (percent)	4.21%
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	$ 47,871
Securities available-for-sale, weighted average yield (percent)	3.91%

Debt Securities, Available-for-sale, Weighted Average Yield

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