INVESTMENT SECURITIES - Allowance for credit losses to HTM securities (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
		Jun. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Allowance for credit losses:
Beginning balance			$ 0
Impact of ASU 2016-13 adoption(1)		$ 242,242	242,242	$ 239,822	$ 240,864	$ 228,024	$ 223,266	$ 219,041
Total ending allowance balance		71	71
Cumulative change in accounting principle
Allowance for credit losses:
Impact of ASU 2016-13 adoption(1)	[1]				$ (5,319)
Corporate bonds
Allowance for credit losses:
Beginning balance		71	0
Provision for credit losses		0	0
Securities charged-off (recoveries)		0	0
Total ending allowance balance		71	71
Corporate bonds | Cumulative change in accounting principle
Allowance for credit losses:
Beginning balance			71
Corporate CMO
Allowance for credit losses:
Beginning balance		0	0
Provision for credit losses		0	0
Securities charged-off (recoveries)		0	0
Total ending allowance balance		$ 0	0
Corporate CMO | Cumulative change in accounting principle
Allowance for credit losses:
Beginning balance			$ 0

[1] Refer to Note 1 - Organization and Summary of Significant Accounting Policies for further information.