SECURITIES (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Accrued interest receivable	$ 20,800
Securities held to maturity with unrealized losses	0	$ 0
Carrying value of held to maturity securities	855
Gross gain on held to maturity securities	201
Reclassification from held to maturity securities	(88,890)	(91,324)
Reclassification to debt securities available for sale	6,108,346	3,294,361
Equity securities with a readily determinable fair value	19,629	18,435
Equity securities with a readily determinable fair value	19,629	18,435
Unrealized gain on equity securities, net	640	525	$ 212
FHLB stock	19,500	16,800
Obligations of states and political subdivisions
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Reclassification from held to maturity securities	(88,890)	(91,324)
Reclassification to debt securities available for sale	1,635,227	$ 707,190
Collateral Pledged
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Securities pledged as collateral	$ 2,120,000

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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 restricted 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 measured at fair value with change in fair value recognized in net income (FV-NI).

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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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