SECURITIES (Debt securities available for sale) (Details) $ in Thousands	Jun. 30, 2020 USD ($) numberOfBankLocations	Dec. 31, 2019 USD ($) numberOfBankLocations
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 1,174,109	$ 1,619,266
Fair Value, 12 months or longer	392,756	241,232
Fair Value, Total	1,566,865	1,860,498
Unrealized Losses, Less than 12 months	(26,405)	(23,588)
Unrealized Losses, 12 months or longer	(18,367)	(4,814)
Unrealized Losses, Total	$ (44,772)	$ (28,402)
Count, Less than 12 months \| numberOfBankLocations	178	200
Count, 12 months or longer \| numberOfBankLocations	19	58
Count, Total \| numberOfBankLocations	197	258
Mortgage and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 1,070,001	$ 1,231,732
Fair Value, 12 months or longer	392,756	241,232
Fair Value, Total	1,462,757	1,472,964
Unrealized Losses, Less than 12 months	(23,591)	(14,189)
Unrealized Losses, 12 months or longer	(18,367)	(4,814)
Unrealized Losses, Total	$ (41,958)	$ (19,003)
Count, Less than 12 months \| numberOfBankLocations	81	150
Count, 12 months or longer \| numberOfBankLocations	19	58
Count, Total \| numberOfBankLocations	100	208
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 104,108	$ 387,534
Fair Value, 12 months or longer	0	0
Fair Value, Total	104,108	387,534
Unrealized Losses, Less than 12 months	(2,814)	(9,399)
Unrealized Losses, 12 months or longer	0	0
Unrealized Losses, Total	$ (2,814)	$ (9,399)
Count, Less than 12 months \| numberOfBankLocations	97	50
Count, 12 months or longer \| numberOfBankLocations	0	0
Count, Total \| numberOfBankLocations	97	50

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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