FAIR VALUE DISCLOSURES - Summary of Financial Assets and Liabilities Measure at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets
Derivatives	$ 27,567	$ 12,682
Investment securities available-for-sale	2,654,909	1,349,408
Liabilities
Derivatives	27,565	12,687
Fair Value, Measurements, Recurring
Assets
Derivatives	28,113	12,757
Investment securities available-for-sale	2,654,909	1,349,408
Total	2,683,022	1,362,165
Liabilities
Derivatives	27,624	12,755
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 1
Assets
Derivatives	0	0
Investment securities available-for-sale	7,737	2,969
Total	7,737	2,969
Liabilities
Derivatives	0	0
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 2
Assets
Derivatives	28,113	12,757
Investment securities available-for-sale	2,647,172	1,346,439
Total	2,675,285	1,359,196
Liabilities
Derivatives	27,624	12,755
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 3
Assets
Derivatives	0	0
Investment securities available-for-sale	0	0
Total	0	0
Liabilities
Derivatives	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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