FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value By Balance Sheet Location) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets:
Securities—trading	$ 24,753	$ 24,568
Securities—available-for-sale	1,223,764	800,917
Securities—held-to-maturity	269,402	270,528
Liabilities:
FHLB advances at fair value	213	54,216
Carrying Value
Assets:
Cash and cash equivalents	300,708	247,719
Securities—trading	24,753	24,568
Securities—available-for-sale	1,223,764	800,917
Securities—held-to-maturity	266,391	267,873
Loans receivable held for sale	86,707	246,353
Loans receivable	7,421,255	7,451,148
FHLB stock	10,334	12,506
Bank-owned life insurance	159,948	158,936
Mortgage servicing rights	15,272	15,249
Liabilities:
Demand, interest checking and money market accounts	5,685,219	5,552,690
Regular savings	1,592,023	1,523,391
Certificates of deposit	1,144,718	1,045,333
FHLB advances at fair value	213	54,216
Other borrowings	120,245	105,685
Junior subordinated debentures at fair value	96,040	95,200
Estimated Fair Value
Assets:
Cash and cash equivalents	300,708	247,719
Securities—trading	24,753	24,568
Securities—available-for-sale	1,223,764	800,917
Securities—held-to-maturity	269,402	270,528
Loans receivable held for sale	87,937	246,815
Loans receivable	7,303,871	7,337,608
FHLB stock	10,334	12,506
Bank-owned life insurance	159,948	158,936
Mortgage servicing rights	18,846	16,740
Liabilities:
Demand, interest checking and money market accounts	5,685,219	5,552,690
Regular savings	1,592,023	1,523,391
Certificates of deposit	1,127,412	1,028,866
FHLB advances at fair value	213	54,216
Other borrowings	120,245	105,685
Junior subordinated debentures at fair value	96,040	95,200
Interest rate swaps [Member] | Carrying Value
Assets:
Derivatives:	7,268	8,330
Liabilities:
Derivatives:	7,268	8,330
Interest rate swaps [Member] | Estimated Fair Value
Assets:
Derivatives:	7,268	8,330
Liabilities:
Derivatives:	7,268	8,330
Interest Rate Forward Sales Commitments [Member] | Carrying Value
Assets:
Derivatives:	628	482
Liabilities:
Derivatives:	337	289
Interest Rate Forward Sales Commitments [Member] | Estimated Fair Value
Assets:
Derivatives:	628	482
Liabilities:
Derivatives:	$ 337	$ 289