FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value By Balance Sheet Location) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets:
Securities—trading	$ 33,994	$ 34,134
Securities—available-for-sale	1,199,279	1,138,573
Securities—held-to-maturity	255,823	226,627
Liabilities:
FHLB advances at fair value	75,400	133,381
Level 1 [Member] | Carrying Value
Assets:
Cash and cash equivalents	260,570	261,917
Bank-owned life insurance	156,928	156,865
Level 1 [Member] | Estimated Fair Value
Assets:
Cash and cash equivalents	260,570	261,917
Bank-owned life insurance	156,928	156,865
Level 2 and Level 3 [Member] | Carrying Value
Assets:
Securities—trading	33,994	34,134
Level 2 and Level 3 [Member] | Estimated Fair Value
Assets:
Securities—trading	33,994	34,134
Level 2 [Member] | Carrying Value
Assets:
Securities—available-for-sale	1,199,279	1,138,573
Loans receivable held for sale	47,523	44,712
Liabilities:
Demand, interest checking and money market accounts	5,414,431	5,416,556
Regular savings	1,327,558	1,284,642
Certificates of deposit	1,287,873	1,353,870
FHLB advances at fair value	75,400	133,381
Other borrowings	106,132	98,325
Level 2 [Member] | Estimated Fair Value
Assets:
Securities—available-for-sale	1,199,279	1,138,573
Loans receivable held for sale	48,461	45,600
Liabilities:
Demand, interest checking and money market accounts	5,414,431	5,416,556
Regular savings	1,327,558	1,284,642
Certificates of deposit	1,273,897	1,332,825
FHLB advances at fair value	75,400	133,381
Other borrowings	106,132	98,325
Level 2 [Member] | Interest rate swaps [Member] | Carrying Value
Assets:
Derivatives:	18,959	11,984
Liabilities:
Derivatives:	18,959	11,984
Level 2 [Member] | Interest rate swaps [Member] | Estimated Fair Value
Assets:
Derivatives:	18,959	11,984
Liabilities:
Derivatives:	18,959	11,984
Level 2 [Member] | Interest Rate Forward Sales Commitments [Member] | Carrying Value
Assets:
Derivatives:	1,067	471
Liabilities:
Derivatives:	417	50
Level 2 [Member] | Interest Rate Forward Sales Commitments [Member] | Estimated Fair Value
Assets:
Derivatives:	1,067	471
Liabilities:
Derivatives:	417	50
Level 3 [Member] | Carrying Value
Assets:
Securities—held-to-maturity	246,320	220,666
Loans receivable	7,107,802	7,314,504
FHLB stock	13,347	16,057
Mortgage servicing rights	13,676	13,295
Liabilities:
Junior subordinated debentures at fair value	92,879	92,480
Level 3 [Member] | Estimated Fair Value
Assets:
Securities—held-to-maturity	255,823	226,627
Loans receivable	6,982,492	7,084,631
FHLB stock	13,347	16,057
Mortgage servicing rights	15,983	17,370
Liabilities:
Junior subordinated debentures at fair value	$ 92,879	$ 92,480