SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 948,639	$ 947,597
Gross Unrealized Gains	15,513	10,480
Gross Unrealized (Losses)	(3,615)	(11,313)
Estimated Fair Value	960,537	946,764
Obligations of States and Political Subdivisions
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	270,206	274,007
Gross Unrealized Gains	9,087	4,962
Gross Unrealized (Losses)	(753)	(3,079)
Estimated Fair Value	278,540	275,890
Corporate and Other Bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	116,318	123,674
Gross Unrealized Gains	1,009	892
Gross Unrealized (Losses)	(909)	(2,786)
Estimated Fair Value	116,418	121,780
Mortgage-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	548,229	536,031
Gross Unrealized Gains	5,417	4,626
Gross Unrealized (Losses)	(1,895)	(5,371)
Estimated Fair Value	551,751	535,286
Other Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,886	13,885
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(58)	(77)
Estimated Fair Value	$ 13,828	$ 13,808

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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