DEPOSITS (Deposit Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Deposits:
Non-interest-bearing accounts	$ 6,494,852	$ 6,385,177
Interest-bearing checking	1,971,936	1,947,414
Regular savings accounts	2,853,891	2,784,716
Money market accounts	2,402,731	2,370,995
Total interest-bearing transaction and saving accounts	7,228,558	7,103,125
Certificates of deposit less than or equal to $250,000	623,336	657,615
Certificates of deposit greater than $250,000	177,028	181,016
Total certificates of deposit	800,364	838,631
Total deposits	14,523,774	14,326,933
Included in total deposits:
Public fund transaction and savings accounts	355,599	353,874
Public fund interest-bearing certificates	37,689	39,961
Total public deposits	$ 393,288	$ 393,835