SECURITIES (Securities available for sale) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,552,214	$ 2,492,620
Gross Unrealized Gains	25,617	4,662
Gross Unrealized Losses	(15,944)	(46,573)
Securities available for sale	2,561,887	2,450,709
Equity securities with a readily determinable fair value	18,157	17,086
Total debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,534,057	2,475,534
Gross Unrealized Gains	25,617	4,662
Gross Unrealized Losses	(15,944)	(46,573)
Securities available for sale	2,543,730	2,433,623
U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	18,660	32,075
Gross Unrealized Gains	48	3
Gross Unrealized Losses	(87)	(127)
Securities available for sale	18,621	31,951
Mortgage and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,191,327	2,061,358
Gross Unrealized Gains	17,472	3,740
Gross Unrealized Losses	(15,473)	(38,400)
Securities available for sale	2,193,326	2,026,698
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	324,070	382,101
Gross Unrealized Gains	8,097	919
Gross Unrealized Losses	(384)	(8,046)
Securities available for sale	$ 331,783	$ 374,974

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) 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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Amortized cost 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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