Loans and Allowance for Loan Losses - Schedule of Average Balance (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Financing Receivable Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment, Total	$ 121,139	$ 100,704
Commercial [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	23,688	20,714
Average Recorded Investment with an allowance recorded	11,347	7,468
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	5,477
Average Recorded Investment with an allowance recorded	8,690	905
Commercial Real Estate - Other [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	40,135	40,801
Average Recorded Investment with an allowance recorded	26,279	23,672
Residential [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	2,289	2,275
Average Recorded Investment with an allowance recorded	881	910
Consumer [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	660	1,842
Average Recorded Investment with an allowance recorded	$ 1,693	$ 2,117

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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=84173941&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=84173941&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=84173941&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=84173941&loc=d3e5212-111524

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