SECURITIES (Debt securities available for sale) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 560,401	$ 793,718
Fair Value, 12 months or longer	496,907	1,067,809
Fair Value, Total	1,057,308	1,861,527
Unrealized Losses, Less than 12 months	(5,363)	(9,533)
Unrealized Losses, 12 months or longer	(10,581)	(37,040)
Unrealized Losses, Total	(15,944)	(46,573)
U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	4,631	24,902
Fair Value, 12 months or longer	0	4,577
Fair Value, Total	4,631	29,479
Unrealized Losses, Less than 12 months	(87)	(83)
Unrealized Losses, 12 months or longer	0	(44)
Unrealized Losses, Total	(87)	(127)
Mortgage and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	544,795	733,826
Fair Value, 12 months or longer	448,159	805,089
Fair Value, Total	992,954	1,538,915
Unrealized Losses, Less than 12 months	(5,265)	(9,060)
Unrealized Losses, 12 months or longer	(10,208)	(29,340)
Unrealized Losses, Total	(15,473)	(38,400)
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	10,975	34,990
Fair Value, 12 months or longer	48,748	258,143
Fair Value, Total	59,723	293,133
Unrealized Losses, Less than 12 months	(11)	(390)
Unrealized Losses, 12 months or longer	(373)	(7,656)
Unrealized Losses, Total	$ (384)	$ (8,046)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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