INVESTMENTS - Schedule of Maturities of Investment Securities Available-for-Sale and Held-to-Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Available for Sale, Amortized Cost
Within one year	$ 2,744	$ 0
After one year but within five years	104,877	103,960
After five years but within ten years	241,045	204,186
After ten years	5,554,884	4,941,736
Available-for-sale, amortized cost total	5,903,550	5,249,882
Available for Sale, Fair Value
Within one year	2,744	0
After one year but within five years	103,153	107,009
After five years but within ten years	224,031	204,289
After ten years	5,166,001	4,894,013
Available-for-sale, fair value total	5,495,929	5,205,311
Held to Maturity, Amortized Cost
Within one year	1,031	232
After one year but within five years	2,674	2,675
After five years but within ten years	38,696	44,137
After ten years	42,501	43,602
Held-to-maturity, amortized cost total	84,902	90,646
Held to Maturity, Fair Value
Within one year	1,031	234
After one year but within five years	2,689	2,736
After five years but within ten years	39,217	45,404
After ten years	42,817	45,757
Held-to-maturity, fair value total	$ 85,754	$ 94,131