INVESTMENT SECURITIES - Investments in Debt and Equity Securities Reported Less than Historical Cost (Details) - Investments reported at less than historical cost - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Historical cost	$ 1,915,960	$ 2,207,633
Fair value	1,646,132	1,910,508
Gross unrealized losses	$ 269,828	$ 297,125
Percent of the Corporation's investments available for sale	99.70%	96.70%