FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value By Balance Sheet Location) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Assets:
Securities—trading	$ 33,753		$ 34,134
Securities—available-for-sale	1,177,757		1,138,573
Securities—held-to-maturity	267,501	$ 267,501	226,627
Liabilities:
FHLB advances at fair value	325,383		133,381
Carrying Value
Assets:
Cash and cash equivalents	234,656		261,917
Securities—trading	33,753		34,134
Securities—available-for-sale	1,177,757		1,138,573
Securities—held-to-maturity	254,666		220,666
Loans receivable held for sale	113,230		44,712
Loans receivable	7,325,925		7,314,504
FHLB stock	23,347		16,057
Bank-owned life insurance	158,001		156,865
Mortgage servicing rights	14,276		13,295
Liabilities:
Demand, interest checking and money market accounts	5,389,585		5,416,556
Regular savings	1,321,518		1,284,642
Certificates of deposit	1,208,671		1,353,870
FHLB advances at fair value	325,383		133,381
Other borrowings	112,308		98,325
Junior subordinated debentures at fair value	93,298		92,480
Estimated Fair Value
Assets:
Cash and cash equivalents	234,656		261,917
Securities—trading	33,753		34,134
Securities—available-for-sale	1,177,757		1,138,573
Securities—held-to-maturity	267,501		226,627
Loans receivable held for sale	115,794		45,600
Loans receivable	7,224,842		7,084,631
FHLB stock	23,347		16,057
Bank-owned life insurance	158,001		156,865
Mortgage servicing rights	15,457		17,370
Liabilities:
Demand, interest checking and money market accounts	5,389,585		5,416,556
Regular savings	1,321,518		1,284,642
Certificates of deposit	1,197,199		1,332,825
FHLB advances at fair value	325,383		133,381
Other borrowings	112,308		98,325
Junior subordinated debentures at fair value	93,298		92,480
Interest rate swaps [Member] | Carrying Value
Assets:
Derivatives:	21,670		11,984
Liabilities:
Derivatives:	21,670		11,984
Interest rate swaps [Member] | Estimated Fair Value
Assets:
Derivatives:	21,670		11,984
Liabilities:
Derivatives:	21,670		11,984
Interest Rate Forward Sales Commitments [Member] | Carrying Value
Assets:
Derivatives:	1,544		471
Liabilities:
Derivatives:	904		50
Interest Rate Forward Sales Commitments [Member] | Estimated Fair Value
Assets:
Derivatives:	1,544		471
Liabilities:
Derivatives:	$ 904		$ 50