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Fair Value - Reconciliation of All Assets Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pooled trust preferred securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 7,913	$ 8,222
Accretion of discount	5	4
Sales/payments received	(15)	(17)
Increase (decrease) in fair value of securities	307	(787)
Balance at end of period	8,210	7,422
States and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	0	40
Accretion of discount	0	0
Sales/payments received	0	(40)
Increase (decrease) in fair value of securities	0	0
Balance at end of period	$ 0	$ 0

X

- Definition

Fair value, measurement with unobservable inputs reconciliation, recurring basis, asset, increase (decrease) in fair value of securities.

+ References

No definition available.

+ Details

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X

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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X

- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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X

- Definition

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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X

- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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