Loans and Leases - Summary of Troubled Debt Restructurings by Class of Loans (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) Contract	Dec. 31, 2016 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	772	679
Pre-Modification Outstanding Recorded Investment	$ 13,954	$ 12,220
Post- Modification Outstanding Recorded Investment	$ 12,570	$ 11,222
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	3	4
Pre-Modification Outstanding Recorded Investment	$ 1,608	$ 778
Post- Modification Outstanding Recorded Investment	$ 1,683	$ 737
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	3	3
Pre-Modification Outstanding Recorded Investment	$ 3,568	$ 1,727
Post- Modification Outstanding Recorded Investment	$ 3,091	$ 1,504
Total commercial loans and leases
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	6	7
Pre-Modification Outstanding Recorded Investment	$ 5,176	$ 2,505
Post- Modification Outstanding Recorded Investment	$ 4,774	$ 2,241
Direct installment
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	641	527
Pre-Modification Outstanding Recorded Investment	$ 5,107	$ 6,090
Post- Modification Outstanding Recorded Investment	$ 4,500	$ 5,566
Residential mortgages
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	43	45
Pre-Modification Outstanding Recorded Investment	$ 2,251	$ 2,155
Post- Modification Outstanding Recorded Investment	$ 2,095	$ 2,081
Indirect installment
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	18	19
Pre-Modification Outstanding Recorded Investment	$ 48	$ 51
Post- Modification Outstanding Recorded Investment	$ 43	$ 51
Consumer lines of credit
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	64	81
Pre-Modification Outstanding Recorded Investment	$ 1,372	$ 1,419
Post- Modification Outstanding Recorded Investment	$ 1,158	$ 1,283
Total consumer loans
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	766	672
Pre-Modification Outstanding Recorded Investment	$ 8,778	$ 9,715
Post- Modification Outstanding Recorded Investment	$ 7,796	$ 8,981

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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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