INVESTMENTS (Schedule of Amortized Cost and Estimated Fair Values of Debt Securities by Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Available-for-sale, Amortized Cost
Due in one year or less	$ 1,217
Due after one year through five years	8,625
Due after five years through ten years	88,087
Due after ten years	46,676
Subtotal	144,605
Mortgage-related securities	1,371,452
Available-for-sale securities, book value	1,516,057	$ 1,508,981
Available-for-sale, Fair Value
Due in one year or less	1,227
Due after one year through five years	8,560
Due after five years through ten years	86,586
Due after ten years	44,707
Subtotal	141,080
Mortgage-related securities	1,280,729
Fair value, total	$ 1,421,809	$ 1,507,486