Loans and Allowance for Loan Losses - Schedule of Average Balance (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment, Total	$ 113,868	$ 108,923	$ 116,739	$ 107,820
Commercial [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	23,242	20,228	21,585	20,073
Average Recorded Investment with an allowance recorded	13,965	11,846	15,997	10,091
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	10,996		5,519
Average Recorded Investment with an allowance recorded	3,160	4,675	8,294	4,675
Commercial Real Estate - Other [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	34,387	43,893	35,378	41,771
Average Recorded Investment with an allowance recorded	22,493	21,439	24,368	24,246
Residential [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	2,325	2,189	2,309	2,274
Average Recorded Investment with an allowance recorded	866	942	874	918
Consumer [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	1,076	1,741	838	1,722
Average Recorded Investment with an allowance recorded	$ 1,358	$ 1,970	$ 1,577	$ 2,050

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+ 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

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-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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+ 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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