SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,571,735	$ 971,339
Gross Unrealized Gains	7,528	10,569
Gross Unrealized (Losses)	(21,215)	(7,686)
Estimated Fair Value	1,558,048	974,222
Obligations of States and Political Subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	525,328	295,546
Gross Unrealized Gains	5,635	6,842
Gross Unrealized (Losses)	(2,379)	(564)
Estimated Fair Value	528,584	301,824
Corporate and Other Bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	148,933	113,625
Gross Unrealized Gains	681	1,131
Gross Unrealized (Losses)	(1,166)	(876)
Estimated Fair Value	148,448	113,880
Mortgage-Backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	885,734	552,431
Gross Unrealized Gains	1,212	2,596
Gross Unrealized (Losses)	(17,512)	(6,169)
Estimated Fair Value	869,434	548,858
Other Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,740	9,737
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(158)	(77)
Estimated Fair Value	$ 11,582	$ 9,660

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

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

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

+ References

No definition available.

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- Definition

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.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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