SECURITIES (Securities available for sale debt maturities) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Amortized Cost
Due in 1 year or less	$ 13,286
Due in 1 to 5 years	18,199
Due in 5 to 10 years	198,036
Due after 10 years	1,628,518
Total debt securities	1,858,039
Mortgage and asset-backed securities	4,584,993
Equity securities with a readily determinable fair value	20,651	$ 19,629
Total investment securities	6,463,683
Estimated Fair Value
Due in 1 year or less	13,351
Due in 1 to 5 years	19,153
Due in 5 to 10 years	202,564
Due after 10 years	1,676,920
Total debt securities	1,911,988
Mortgage and asset-backed securities	4,611,339
Equity securities with a readily determinable fair value	20,651
Total investment securities	$ 6,543,978

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27198-111563