FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value By Balance Sheet Location) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets:
Securities—trading	$ 27,886	$ 26,981
Debt Securities, Available-for-sale	3,094,422	3,638,993
Securities—held-to-maturity	1,036,301	541,853
Securities purchased under agreements to resell	300,000	300,000
Liabilities:
FHLB advances at fair value	0	50,000
Subordinated notes, net	98,752	98,564
Carrying Value
Assets:
Cash and cash equivalents	1,170,847	2,134,300
Securities—trading	27,886	26,981
Debt Securities, Available-for-sale	3,094,422	3,638,993
Securities purchased under agreements to resell	300,000	300,000
Loans receivable held for sale	69,161	96,487
Loans receivable	9,456,829	9,084,763
Equity securities	584	1,000
FHLB stock	10,000	12,000
Bank-owned life insurance	293,631	244,156
Mortgage servicing rights	16,618	16,045
SBA servicing asset	1,015	1,161
Investments in limited partnerships	11,881	10,257
Liabilities:
Demand, interest checking and money market accounts	10,655,075	10,703,586
Regular savings	2,801,177	2,784,716
Certificates of deposit	756,312	838,631
FHLB advances at fair value	0	50,000
Other borrowings	234,737	264,490
Subordinated notes, net		98,564
Junior subordinated debentures at fair value	72,229	119,815
Estimated Fair Value
Assets:
Cash and cash equivalents	1,170,847	2,134,300
Securities—trading	27,886	26,981
Debt Securities, Available-for-sale	3,094,422	3,638,993
Securities purchased under agreements to resell	300,000	300,000
Loans receivable held for sale	69,189	96,914
Loans receivable	9,322,390	9,100,516
Equity securities	584	1,298
FHLB stock	10,000	12,000
Bank-owned life insurance	293,631	244,156
Mortgage servicing rights	35,290	24,393
SBA servicing asset	1,015	1,161
Investments in limited partnerships	11,881	10,257
Liabilities:
Demand, interest checking and money market accounts	10,655,075	10,703,586
Regular savings	2,801,177	2,784,716
Certificates of deposit	741,783	836,877
FHLB advances at fair value	0	50,287
Other borrowings	234,737	264,490
Subordinated notes, net	98,263	105,241
Junior subordinated debentures at fair value	72,229	119,815
Interest rate swaps [Member] | Carrying Value
Assets:
Derivatives:	22,229	20,826
Liabilities:
Derivatives:	32,842	11,336
Interest rate swaps [Member] | Carrying Value | Cash Flow Hedging
Liabilities:
Derivatives:	398	279
Interest rate swaps [Member] | Estimated Fair Value
Assets:
Derivatives:	22,229	20,826
Liabilities:
Derivatives:	32,842	11,336
Interest rate swaps [Member] | Estimated Fair Value | Cash Flow Hedging
Liabilities:
Derivatives:	398	279
Interest Rate Forward Sales Commitments [Member] | Carrying Value
Assets:
Derivatives:	470	1,555
Liabilities:
Derivatives:	88	140
Interest Rate Forward Sales Commitments [Member] | Estimated Fair Value
Assets:
Derivatives:	470	1,555
Liabilities:
Derivatives:	88	140
Loan Participations and Assignments | Carrying Value
Liabilities:
Derivatives:	139	0
Loan Participations and Assignments | Estimated Fair Value
Liabilities:
Derivatives:	139	0
Fair Value, Inputs, Level 2 [Member] | Carrying Value
Assets:
Securities—held-to-maturity	1,142,646	464,008
Fair Value, Inputs, Level 2 [Member] | Estimated Fair Value
Assets:
Securities—held-to-maturity	1,026,736	484,483
Fair Value, Inputs, Level 3 [Member] | Carrying Value
Assets:
Securities—held-to-maturity	9,543	57,347
Fair Value, Inputs, Level 3 [Member] | Estimated Fair Value
Assets:
Securities—held-to-maturity	$ 9,565	$ 57,370