INVESTMENTS (Gross Unrealized Losses and Fair Value by Length of Time of Available-For-Sale Securities) (Detail) $ in Thousands	Dec. 31, 2017 USD ($) Securities	Dec. 31, 2016 USD ($) Securities
Schedule Of Available For Sale Securities [Line Items]
Number of Securities \| Securities	79	103
Fair Value	$ 346,417	$ 358,654
Less than 12 months	1,054	7,043
More than 12 months	6,105	345
Total Unrealized Losses	$ 7,159	$ 7,388
Us Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Number of Securities \| Securities	13	12
Fair Value	$ 106,568	$ 96,788
Less than 12 months	545	2,556
More than 12 months	2,236	0
Total Unrealized Losses	$ 2,781	$ 2,556
U S States and Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Number of Securities \| Securities	20	53
Fair Value	$ 18,228	$ 48,010
Less than 12 months	107	516
More than 12 months	62	70
Total Unrealized Losses	$ 169	$ 586
Mortgage Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Number of Securities \| Securities	46	37
Fair Value	$ 221,621	$ 212,844
Less than 12 months	402	3,971
More than 12 months	3,807	198
Total Unrealized Losses	$ 4,209	$ 4,169
Trust Preferred Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Number of Securities \| Securities	0	1
Fair Value	$ 0	$ 1,012
Less than 12 months	0	0
More than 12 months	0	77
Total Unrealized Losses	$ 0	$ 77

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

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