Loans and Allowance for Loan Losses - Schedule of Average Balance of Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment, Total	$ 99,172	$ 105,247	$ 102,230	$ 115,072
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	25,817	32,951	26,038	38,029
Average Recorded Investment with an allowance recorded	8,448	19,546	7,996	17,641
Commercial Real Estate - Other [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	34,682	34,344	32,598	38,197
Average Recorded Investment with an allowance recorded	22,916	12,230	28,911	15,016
Residential [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	2,376	1,348	2,121	1,359
Average Recorded Investment with an allowance recorded	1,147	1,060	1,125	1,035
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with no related allowance	1,717	871	1,420	981
Average Recorded Investment with an allowance recorded	$ 2,069	2,781	$ 2,021	2,695
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment with an allowance recorded		$ 116		$ 119

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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://www.xbrl.org/2003/role/presentationRef
-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://www.xbrl.org/2003/role/presentationRef
-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://www.xbrl.org/2003/role/presentationRef
-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://www.xbrl.org/2003/role/presentationRef
-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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+ References

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