Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount 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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Amount of realized gain (loss) 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 of investment in equity security without readily determinable fair value.

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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SECURITIES (Narrative) (Details) - USD ($)	6 Months Ended
SECURITIES (Narrative) (Details) - USD ($)	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Investment [Line Items]
Held to maturity securities	$ (88,166,000)			$ (236,283,000)
Securities available for sale	2,561,887,000			2,450,709,000
Fair value of securities pledged	569,700,000			524,800,000
Gross realized gains or losses on sale of securities	0	$ 0
Equity securities without readily determinable fair value	18,200,000			17,100,000
Amortized cost of FHLBs	$ 14,900,000			$ 16,600,000
ASU 2017-12
Investment [Line Items]
Held to maturity securities			$ 148,000,000.0
Securities available for sale			$ 148,000,000