Loans and Allowance for Loan Losses - Schedule of Average Balance (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment, Total	$ 116,818	$ 111,359	$ 100,772
Commercial [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	22,629	21,295	24,780
Average Recorded Investment with an allowance recorded	15,816	9,546	7,002
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	6,465
Average Recorded Investment with an allowance recorded	6,912	7,365	453
Commercial Real Estate - Other [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	39,401	39,902	34,632
Average Recorded Investment with an allowance recorded	20,420	27,317	26,562
Residential [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	2,052	2,305	2,415
Average Recorded Investment with an allowance recorded	981	840	1,012
Consumer [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	923	832	1,761
Average Recorded Investment with an allowance recorded	$ 1,219	$ 1,957	$ 2,155

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5258-111524

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Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5258-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

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