Loans and Leases - Summary of Troubled Debt Restructurings by Class of Loans and Leases, Payment Default (Detail) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015 USD ($) Contract	Sep. 30, 2014 USD ($) Contract	Sep. 30, 2015 USD ($) Contract	Sep. 30, 2014 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts		25	47	88	87
Recorded Investment | $	[1]	$ 168	$ 449	$ 657	$ 826
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts				1
Recorded Investment | $	[1]			$ 204
Total Commercial Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts				1
Recorded Investment | $	[1]			$ 204
Direct Installment [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts		22	41	75	80
Recorded Investment | $	[1]	$ 87	$ 356	$ 254	$ 732
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts		2	2	5	2
Recorded Investment | $	[1]	$ 75	$ 33	$ 179	$ 33
Indirect Installment [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts		1	3	6	4
Recorded Investment | $	[1]	$ 6	$ 10	$ 12	$ 11
Consumer Lines of Credit [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts			1	1	1
Recorded Investment | $	[1]		$ 50	$ 8	$ 50

[1] The recorded investment is as of period end.