FAIR VALUE MEASUREMENTS (Details 3) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity Securities		$ 497,688	$ 487,076
Loans and Leases Receivable, Net Amount		6,294,910	5,938,039
Securities held to maturity, fair value		494,194	485,650
Federal Home Loan Bank Stock		11,597	11,497
Bank Owned Life Insurance		151,528	144,503
Liabilities, Fair Value Disclosure [Abstract]
Advances from Federal Home Loan Banks		53,264	50,819
Junior subordinated debentures		73,073	73,107
Subordinated Debt		34,682	34,635
Deposits [Member]
Liabilities, Fair Value Disclosure [Abstract]
Financial Liabilities Book Value	[1]	6,084,952	5,763,101
Accrued Liabilities, Fair Value Disclosure	[1]	6,084,952	5,763,101
Bank Time Deposits [Member]
Liabilities, Fair Value Disclosure [Abstract]
Financial Liabilities Book Value	[2]	644,301	649,152
Accrued Liabilities, Fair Value Disclosure	[2]	639,060	647,038
Federal Home Loan Bank Advances [Member]
Liabilities, Fair Value Disclosure [Abstract]
Advances from Federal Home Loan Banks	[2]	53,264	50,819
Federal Home Loan Bank Borrowings, Fair Value Disclosure	[2]	52,111	50,898
Customer Repurchase Agreements [Member]
Liabilities, Fair Value Disclosure [Abstract]
Customer Repurchase Agreements and other short-term borrowings	[2]	162,679	176,913
Accrued Liabilities, Fair Value Disclosure	[2]	162,679	176,913
Junior Subordinated Debt [Member]
Liabilities, Fair Value Disclosure [Abstract]
Junior subordinated debentures	[3]	73,073	73,107
Accrued Liabilities, Fair Value Disclosure	[3]	74,680	72,510
Subordinated Debt [Member]
Liabilities, Fair Value Disclosure [Abstract]
Subordinated Debt	[2]	34,682	34,635
Accrued Liabilities, Fair Value Disclosure	[2]	32,707	34,241
Significant Other Observable Inputs (Level 2) [Member] | Deposits [Member]
Liabilities, Fair Value Disclosure [Abstract]
Accrued Liabilities, Fair Value Disclosure	[1]	6,084,952	5,763,101
Significant Other Observable Inputs (Level 2) [Member] | Bank Time Deposits [Member]
Liabilities, Fair Value Disclosure [Abstract]
Accrued Liabilities, Fair Value Disclosure	[2]	639,060	647,038
Significant Other Observable Inputs (Level 2) [Member] | Federal Home Loan Bank Advances [Member]
Liabilities, Fair Value Disclosure [Abstract]
Federal Home Loan Bank Borrowings, Fair Value Disclosure	[2]	52,111
Accrued Liabilities, Fair Value Disclosure	[2]		50,898
Significant Other Observable Inputs (Level 2) [Member] | Junior Subordinated Debt [Member]
Liabilities, Fair Value Disclosure [Abstract]
Accrued Liabilities, Fair Value Disclosure	[3]	74,680	72,510
Significant Unobservable Inputs (Level 3) [Member] | Customer Repurchase Agreements [Member]
Liabilities, Fair Value Disclosure [Abstract]
Accrued Liabilities, Fair Value Disclosure	[2]	162,679	176,913
Significant Unobservable Inputs (Level 3) [Member] | Subordinated Debt [Member]
Liabilities, Fair Value Disclosure [Abstract]
Accrued Liabilities, Fair Value Disclosure	[2]	32,707	34,241
US Treasury Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity Securities	[4]	1,006	1,007
Securities held to maturity, fair value	[4]	1,035	1,054
US Treasury Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Securities held to maturity, fair value	[4]	1,035	1,054
Agency mortgage-backed securities
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity Securities	[4]	204,768	156,088
Securities held to maturity, fair value	[4]	205,823	157,504
Agency mortgage-backed securities | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Securities held to maturity, fair value	[4]	205,823	157,504
Agency collateralized mortgage obligations
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity Securities	[4]	262,998	297,445
Securities held to maturity, fair value	[4]	258,408	294,650
Agency collateralized mortgage obligations | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Securities held to maturity, fair value	[4]	258,408	294,650
Single issuer trust preferred securities issued by banks and insurers
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity Securities	[4]	1,500	1,500
Securities held to maturity, fair value	[4]	1,529	1,544
Single issuer trust preferred securities issued by banks and insurers | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Securities held to maturity, fair value	[4]	1,529	1,544
Small Business Administration Pooled Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Held-to-maturity Securities	[4]	27,416	31,036
Securities held to maturity, fair value	[4]	27,399	30,898
Small Business Administration Pooled Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Securities held to maturity, fair value	[4]	0	0
Small Business Administration Pooled Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Securities held to maturity, fair value	[4]	27,399	30,898
Small Business Administration Pooled Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Securities held to maturity, fair value	[4]	0	0
Loans Net Of Allowance For Loan Loses [Member]
Assets, Fair Value Disclosure [Abstract]
Loans and Leases Receivable, Net Amount	[5]	6,261,343	5,904,065
Loans, net of allowance for loan losses	[5]	6,116,051	5,784,778
Loans Net Of Allowance For Loan Loses [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Loans, net of allowance for loan losses	[5]	6,116,051	5,784,778
Investment in Federal Home Loan Bank Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Federal Home Loan Bank Stock	[6]	11,597	11,497
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	[6]	11,597	11,497
Investment in Federal Home Loan Bank Stock [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	[6]	0	0
Investment in Federal Home Loan Bank Stock [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	[6]	11,597	11,497
Investment in Federal Home Loan Bank Stock [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	[6]	0	0
Cash Surrender Value [Member]
Assets, Fair Value Disclosure [Abstract]
Bank Owned Life Insurance	[7]	151,528	144,503
Cash Surrender Value, Fair Value Disclosure	[7]	151,528	144,503
Cash Surrender Value [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash Surrender Value, Fair Value Disclosure	[7]	0	0
Cash Surrender Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash Surrender Value, Fair Value Disclosure	[7]	151,528	144,503
Cash Surrender Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets, Fair Value Disclosure [Abstract]
Cash Surrender Value, Fair Value Disclosure	[7]	$ 0	$ 0

[1] Fair value of demand deposits, savings and interest checking accounts and money market deposits is the amount payable on demand at the reporting date.

[2] Fair value was determined by discounting anticipated future cash payments using rates currently available for instruments with similar remaining maturities.

[3] Fair value was determined based upon market prices of securities with similar terms and maturities.

[4] The fair values presented are based on quoted market prices, where available. If quoted market prices are not available, fair values are based on quoted market prices of comparable instruments and/or discounted cash flow analysis.

[5] Fair value is estimated by discounting the future cash flows using the current rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining maturities or cash flows. Additionally, this amount excludes collateral dependent impaired loans, which are deemed to be marked to fair value on a nonrecurring basis.

[6] FHLB stock has no quoted market value and is carried at cost, therefore the carrying amount approximates fair value.

[7] Cash surrender value of life insurance is recorded at its cash surrender value (or the amount that can be realized upon surrender of the policy), therefore carrying amount approximates fair value.