INVESTMENTS (Schedule of Amortized Cost and Estimated Fair Values of Debt Securities by Contractual Maturity) (Details) $ in Thousands	Jun. 30, 2021 USD ($)
Available-for-sale, Amortized Cost
Due in one year or less	$ 3,018
Due after one year through five years	4,276
Due after five years through ten years	74,599
Due after ten years	47,116
Subtotal	129,009
Mortgage-related securities	1,252,855
Total	1,381,864
Available-for-sale, Fair Value
Due in one year or less	3,072
Due after one year through five years	4,641
Due after five years through ten years	77,814
Due after ten years	49,453
Subtotal	134,980
Mortgage-related securities	1,264,843
Fair value, total	$ 1,399,823