INVESTMENT SECURITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-Sale Portfolio [Abstract]
Amortized cost	$ 2,742,278	$ 2,397,886
Gross unrealized gains	69,254	77,293
Gross unrealized losses	3,419	2,254
Estimated fair value	2,808,113	2,472,925
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	2,742,028
Estimated fair value	2,807,714
Other Securities [Abstract]
Amortized cost	39,827	40,049
Estimated fair value	39,827	40,049
U.S. Treasury and Agency Securities [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	1,866,819	1,479,134
Gross unrealized gains	35,186	39,509
Gross unrealized losses	2,027	910
Estimated fair value	1,899,978	1,517,733
Obligations of State and Political Subdivisions [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	640,455	645,398
Gross unrealized gains	26,487	26,749
Gross unrealized losses	59	244
Estimated fair value	666,883	671,903
Government Agency Mortgage-Backed Securities [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	205,220	228,971
Gross unrealized gains	6,906	9,782
Gross unrealized losses	1,261	1,025
Estimated fair value	210,865	237,728
Corporate Debt Securities [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	16,672	26,803
Gross unrealized gains	66	363
Gross unrealized losses	58	75
Estimated fair value	16,680	27,091
Government Agency Collateralized Mortgage Obligations [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	12,862	17,330
Gross unrealized gains	446	695
Gross unrealized losses	0	0
Estimated fair value	13,308	18,025
Marketable Equity Security [Member]
Available For Sale Equity Securities Amortized Cost Basis [Abstract]
Amortized cost	250	250
Gross unrealized gains	163	195
Gross unrealized losses	14	0
Estimated fair value	399	445
Federal Home Loan Bank Common Stock [Member]
Other Securities [Abstract]
Amortized cost	19,317	19,553
Estimated fair value	19,317	19,553
Federal Reserve Bank Common Stock [Member]
Other Securities [Abstract]
Amortized cost	16,050	16,050
Estimated fair value	16,050	16,050
Other Equity Securities [Member]
Other Securities [Abstract]
Amortized cost	4,460	4,446
Estimated fair value	$ 4,460	$ 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.