FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value By Balance Sheet Location) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets:
Securities—trading	$ 27,354	$ 26,981
Securities—available-for-sale	3,147,547	3,638,993
Securities—held-to-maturity	968,540	541,853
Securities purchased under agreements to resell	300,000	300,000
Liabilities:
FHLB advances at fair value	0	50,000
Subordinated notes, net	98,658	98,564
Carrying Value
Assets:
Cash and cash equivalents	1,988,388	2,134,300
Securities—trading	27,354	26,981
Securities—available-for-sale	3,147,547	3,638,993
Securities purchased under agreements to resell	300,000	300,000
Loans receivable held for sale	64,218	96,487
Loans receivable	9,146,629	9,084,763
Equity securities	893	1,000
FHLB stock	10,000	12,000
Bank-owned life insurance	294,556	244,156
Mortgage servicing rights	16,846	16,045
SBA servicing asset	1,162	1,161
Investments in limited partnerships	10,982	10,257
Liabilities:
Demand, interest checking and money market accounts	10,869,519	10,703,586
Regular savings	2,853,891	2,784,716
Certificates of deposit	800,364	838,631
FHLB advances at fair value	0	50,000
Other borrowings	266,778	264,490
Subordinated notes, net		98,564
Junior subordinated debentures at fair value	70,510	119,815
Estimated Fair Value
Assets:
Cash and cash equivalents	1,988,388	2,134,300
Securities—trading	27,354	26,981
Securities—available-for-sale	3,147,547	3,638,993
Securities purchased under agreements to resell	300,000	300,000
Loans receivable held for sale	64,609	96,914
Loans receivable	9,003,682	9,100,516
Equity securities	893	1,298
FHLB stock	10,000	12,000
Bank-owned life insurance	294,556	244,156
Mortgage servicing rights	32,415	24,393
SBA servicing asset	1,162	1,161
Investments in limited partnerships	10,982	10,257
Liabilities:
Demand, interest checking and money market accounts	10,869,519	10,703,586
Regular savings	2,853,891	2,784,716
Certificates of deposit	790,986	836,877
FHLB advances at fair value	0	50,287
Other borrowings	266,778	264,490
Subordinated notes, net	100,614	105,241
Junior subordinated debentures at fair value	70,510	119,815
Interest rate swaps [Member] | Carrying Value
Assets:
Derivatives:	14,685	20,826
Liabilities:
Derivatives:	18,574	11,336
Interest rate swaps [Member] | Carrying Value | Cash Flow Hedging
Liabilities:
Derivatives:	502	279
Interest rate swaps [Member] | Estimated Fair Value
Assets:
Derivatives:	14,685	20,826
Liabilities:
Derivatives:	18,574	11,336
Interest rate swaps [Member] | Estimated Fair Value | Cash Flow Hedging
Liabilities:
Derivatives:	502	279
Interest Rate Forward Sales Commitments [Member] | Carrying Value
Assets:
Derivatives:	3,062	1,555
Liabilities:
Derivatives:	142	140
Interest Rate Forward Sales Commitments [Member] | Estimated Fair Value
Assets:
Derivatives:	3,062	1,555
Liabilities:
Derivatives:	142	140
Loan Participations and Assignments | Carrying Value
Liabilities:
Derivatives:	218	0
Loan Participations and Assignments | Estimated Fair Value
Liabilities:
Derivatives:	218	0
Fair Value, Inputs, Level 2 [Member] | Carrying Value
Assets:
Securities—held-to-maturity	1,006,234	464,008
Fair Value, Inputs, Level 2 [Member] | Estimated Fair Value
Assets:
Securities—held-to-maturity	958,809	484,483
Fair Value, Inputs, Level 3 [Member] | Carrying Value
Assets:
Securities—held-to-maturity	9,708	57,347
Fair Value, Inputs, Level 3 [Member] | Estimated Fair Value
Assets:
Securities—held-to-maturity	$ 9,731	$ 57,370