Loans - Schedule of Subsequently Defaulted TDRs (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($) SecurityLoan	Mar. 31, 2017 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable
Threshold period for loans in default (in days)	30 days
Non-Covered TDRs \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	65	101
Pre-modification Outstanding Recorded Investment	$ 30,616	$ 13,238
Post-modification Outstanding Recorded Investment	$ 27,200	$ 13,165
Number of loans \| SecurityLoan	122	162
Recorded investment	$ 24,673	$ 28,416
Non-Covered TDRs \| Commercial Loans \| Commercial real estate - Construction \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	1	0
Pre-modification Outstanding Recorded Investment	$ 1,950	$ 0
Post-modification Outstanding Recorded Investment	$ 1,049	$ 0
Number of loans \| SecurityLoan	0	1
Recorded investment	$ 0	$ 117
Non-Covered TDRs \| Commercial Loans \| Commercial real estate - owner-occupied \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	2	3
Pre-modification Outstanding Recorded Investment	$ 10,691	$ 3,004
Post-modification Outstanding Recorded Investment	$ 9,324	$ 2,999
Number of loans \| SecurityLoan	3	9
Recorded investment	$ 10,187	$ 14,732
Non-Covered TDRs \| Commercial Loans \| Commercial real estate - non-owner-occupied \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	9	7
Pre-modification Outstanding Recorded Investment	$ 1,089	$ 1,867
Post-modification Outstanding Recorded Investment	$ 1,091	$ 1,855
Number of loans \| SecurityLoan	9	10
Recorded investment	$ 492	$ 5,041
Non-Covered TDRs \| Commercial Loans \| Commercial and industrial \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	18	15
Pre-modification Outstanding Recorded Investment	$ 14,429	$ 435
Post-modification Outstanding Recorded Investment	$ 13,314	$ 427
Number of loans \| SecurityLoan	29	21
Recorded investment	$ 9,708	$ 4,186
Non-Covered TDRs \| Residential Mortgage \| Residential mortgage \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	0	4
Pre-modification Outstanding Recorded Investment	$ 0	$ 259
Post-modification Outstanding Recorded Investment	$ 0	$ 241
Number of loans \| SecurityLoan	6	22
Recorded investment	$ 598	$ 1,793
Non-Covered TDRs \| Consumer and Other Loans \| Consumer - Home equity \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	14	37
Pre-modification Outstanding Recorded Investment	$ 1,809	$ 6,622
Post-modification Outstanding Recorded Investment	$ 1,795	$ 6,607
Number of loans \| SecurityLoan	24	31
Recorded investment	$ 2,331	$ 1,337
Non-Covered TDRs \| Consumer and Other Loans \| Consumer - Indirect Automobile \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	11	13
Pre-modification Outstanding Recorded Investment	$ 137	$ 184
Post-modification Outstanding Recorded Investment	$ 119	$ 174
Number of loans \| SecurityLoan	34	43
Recorded investment	$ 322	$ 517
Non-Covered TDRs \| Consumer and Other Loans \| Consumer - Other \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of Loans \| SecurityLoan	10	22
Pre-modification Outstanding Recorded Investment	$ 511	$ 867
Post-modification Outstanding Recorded Investment	$ 508	$ 862
Number of loans \| SecurityLoan	17	25
Recorded investment	$ 1,035	$ 693

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Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524

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