SECURITIES (Securities available for sale debt maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Amortized Cost
Due in 1 year or less	$ 22,717
Due in 1 to 5 years	23,369
Due in 5 to 10 years	76,723
Due after 10 years	386,313
Total debt securities	509,122
Mortgage and asset-backed securities	2,465,561
Equity securities with a readily determinable fair value	18,362	$ 17,086
Amortized Cost	2,993,045	2,492,620
Estimated Fair Value
Due in 1 year or less	22,750
Due in 1 to 5 years	23,725
Due in 5 to 10 years	79,411
Due after 10 years	395,643
Total debt securities	521,529
Mortgage and asset-backed securities	2,480,677
Equity securities with a readily determinable fair value	18,362
Total investment securities	$ 3,020,568	$ 2,450,709