Securities - Securities Held to Maturity in Unrecognized Loss Position (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Schedule Of Held To Maturity Securities [Line Items]
Fair value, Less than 12 months	$ 4,253
Unrealized loss, Less than 12 months	(48)
Fair value, 12 months or more	65,640
Unrealized loss, 12 months or more	(3,272)
Total fair value	69,893
Total unrealized loss	(3,320)
Mortgage-Backed Securities (MBS) [Member]
Schedule Of Held To Maturity Securities [Line Items]
Fair value, 12 months or more	62,115
Unrealized loss, 12 months or more	(3,203)
Total fair value	62,115
Total unrealized loss	(3,203)
States and Municipalities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Fair value, Less than 12 months	4,253
Unrealized loss, Less than 12 months	(48)
Fair value, 12 months or more	3,525
Unrealized loss, 12 months or more	(69)
Total fair value	7,778
Total unrealized loss	$ (117)

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for less than 12 months.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
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-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for less than 12 months.

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