INVESTMENT SECURITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-Sale Portfolio [Abstract]
Amortized Cost	$ 2,766,581	$ 2,397,886
Gross Unrealized Gains	102,396	77,293
Gross Unrealized Losses	1,538	2,254
Fair Value	2,867,439	2,472,925
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized Cost	2,766,331
Fair Value	2,867,033
Other Securities [Abstract]
Amortized Cost	49,824	40,049
Fair Value	49,824	40,049
U.S. Treasury and Agency Obligations [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized Cost	1,864,199	1,479,134
Gross Unrealized Gains	69,071	39,509
Gross Unrealized Losses	0	910
Fair Value	1,933,270	1,517,733
Obligations of State and Political Subdivisions [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized Cost	662,774	645,398
Gross Unrealized Gains	24,374	26,749
Gross Unrealized Losses	521	244
Fair Value	686,627	671,903
Government Agency Mortgage-Backed Securities [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized Cost	208,817	228,971
Gross Unrealized Gains	8,087	9,782
Gross Unrealized Losses	968	1,025
Fair Value	215,936	237,728
Corporate Debt Securities [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized Cost	16,705	26,803
Gross Unrealized Gains	115	363
Gross Unrealized Losses	38	75
Fair Value	16,782	27,091
Government Agency Collateralized Mortgage Obligations [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized Cost	13,836	17,330
Gross Unrealized Gains	582	695
Gross Unrealized Losses	0	0
Fair Value	14,418	18,025
Marketable Equity Securities [Member]
Available For Sale Equity Securities Amortized Cost Basis [Abstract]
Amortized Cost	250	250
Gross Unrealized Gains	167	195
Gross Unrealized Losses	11	0
Fair Value	406	445
Federal Home Loan Bank Common Stock [Member]
Other Securities [Abstract]
Amortized Cost	29,500	19,553
Fair Value	29,500	19,553
Federal Reserve Bank Common Stock [Member]
Other Securities [Abstract]
Amortized Cost	16,050	16,050
Fair Value	16,050	16,050
Other Equity Securities [Member]
Other Securities [Abstract]
Amortized Cost	4,274	4,446
Fair Value	$ 4,274	$ 4,446

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.