FAIR VALUE OF FINANCIAL INSTRUMENTS (Assets and Liabilities Measured at Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Fair Value	$ 24,568	$ 34,134
Securities—available-for-sale	800,917	1,138,573
Held-to-maturity Securities, Fair Value	270,528	226,627
Loans receivable held for sale	9,600	0
Advances from FHLB at fair value	54,216	133,381
Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	247,719	261,917
Trading Securities, Fair Value	24,568	34,134
Securities—available-for-sale	800,917	1,138,573
Held-to-maturity Securities, Fair Value	267,873	220,666
Loans receivable held for sale	246,353	44,712
Loans receivable	7,451,148	7,314,504
FHLB stock	12,506	16,057
Bank-owned life insurance	158,936	156,865
MSRs	15,249	13,295
Deposits, Demand NOW and Money Market Accounts, Fair Value Disclosure	5,552,690	5,416,556
Deposits, Savings, Fair Value Disclosure	1,523,391	1,284,642
Deposits, Certificates of Deposit, Fair Value Disclosure	1,045,333	1,353,870
Advances from FHLB at fair value	54,216	133,381
Junior subordinated debentures net of unamortized deferred issuance costs at fair value	95,200	92,480
Other borrowings	105,685	98,325
Reported Value Measurement [Member] | Interest Rate Forward Sales Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	482	471
Derivative liabilities	289	50
Reported Value Measurement [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	8,330	11,984
Derivative liabilities	8,330	11,984
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	247,719	261,917
Trading Securities, Fair Value	24,568	34,134
Securities—available-for-sale	800,917	1,138,573
Held-to-maturity Securities, Fair Value	270,528	226,627
Loans receivable held for sale	246,815	45,600
Loans receivable	7,337,608	7,084,631
FHLB stock	12,506	16,057
Bank-owned life insurance	158,936	156,865
MSRs	16,740	17,370
Deposits, Demand NOW and Money Market Accounts, Fair Value Disclosure	5,552,690	5,416,556
Deposits, Savings, Fair Value Disclosure	1,523,391	1,284,642
Deposits, Certificates of Deposit, Fair Value Disclosure	1,028,866	1,332,825
Advances from FHLB at fair value	54,216	133,381
Junior subordinated debentures net of unamortized deferred issuance costs at fair value	95,200	92,480
Other borrowings	105,685	98,325
Estimate of Fair Value Measurement [Member] | Interest Rate Forward Sales Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	482	471
Derivative liabilities	289	50
Estimate of Fair Value Measurement [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	8,330	11,984
Derivative liabilities	$ 8,330	$ 11,984