Commitments, Contingencies and Derivatives (Commercial Loan Swaps) (Detail) - Interest Rate Swap [Member] swap in Thousands, $ in Thousands	Dec. 31, 2018 USD ($) swap	Dec. 31, 2017 USD ($) swap
Derivative Asset [Abstract]
Derivative, Fair Value, Net	$ (5,682)	$ (7,571)
Notional Amount	$ 43,000	$ 43,000
federal home loan bank 30-day [Member]
Derivative Liability [Abstract]
Derivative Liability, Number of Instruments Held \| swap	57	42
Derivative Liability, Notional Amount	$ 297,624	$ 226,884
Derivative, Net Liability Position, Aggregate Fair Value	$ 7,841	$ 5,036
Derivative Asset [Abstract]
Derivative Asset, Number of Instruments Held \| swap	25	23
Derivative Asset, Notional Amount	$ 118,891	$ 124,784
Derivative, Fair Value, Net	$ 3,467	$ 1,799
Commercial and Industrial Sector [Member]
Derivative Asset [Abstract]
Derivative Asset, Number of Instruments Held \| swap	82	65
Derivative Asset, Notional Amount	$ 416,515	$ 351,668
Derivative, Fair Value, Net	4,374	3,237
Loans [Member]
Derivative Asset [Abstract]
Derivative, Fair Value, Net	$ 0	$ 0
Derivative, Number of Instruments Held \| swap	164	130
Notional Amount	$ 833,030	$ 703,336

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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Nominal or face amount used to calculate payments on the derivative asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959

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The number of derivative instruments of a particular derivative asset or group of derivative assets held by the entity.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 15
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Nominal or face amount used to calculate payments on the derivative liability.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959

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The number of derivative instruments of a particular derivative liability or group of derivative liabilities held by the entity.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Paragraph 4H
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The number of derivative instruments of a particular group held by the entity.

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