INVESTMENT SECURITIES - Investments in Debt and Equity Securities Reported Less than Historical Cost (Details) - Investments reported at less than historical cost - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Historical cost	$ 1,781,108	$ 2,207,633
Fair value	1,560,554	1,910,508
Gross unrealized losses	$ 220,554	$ 297,125
Percent of the Corporation's investments available for sale	95.90%	96.70%