Junior Subordinated Debentures (Narrative) (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2021 USD ($) trust Rate	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
Subordinated Borrowing [Line Items]
Percentage ownership interest in subsidiary trusts	100.00%
Number of unconsolidated subsidiary trusts \| trust	11
Common securities, approximate percentage of junior subordinated debentures	3.00%
Trust preferred securities, approximate percentage of junior subordinated debentures	97.00%
Junior Subordinated Debentures	$ 253,566	$ 253,566	$ 253,566
Period of deferred payment, not to exceed	60 months
Junior Subordinated Debt
Subordinated Borrowing [Line Items]
Junior Subordinated Debentures	$ 253,566	$ 253,600	$ 253,600
Average contractual rate \| Rate	2.32%
Tier two risk based capital	$ 245,500
Interest rate swaps \| Junior Subordinated Debt
Subordinated Borrowing [Line Items]
Notional Amount	$ 210,000
Hedge-adjusted contractual interest rate	3.96%

Weighted average interest rate of debt outstanding.

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

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Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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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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- Definition

Amount of Tier 2 risk-based capital as defined by regulatory framework.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826

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- Definition

Common securities proportion to junior subordinated debentures.

+ References

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- Definition

Debt Instrument, Interest Payment, Deferral Period

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Debt Instrument, Interest Rate, Stated Percentage Adjusted For Hedge

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Number Of Unconsolidated Subsidiary Trusts

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Ownership Interest Percentage In Unconsolidated Subsidiary Trusts

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Trust preferred securities proportion to junior subordinated debentures.

+ References

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