Loans and Leases - Narrative for Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Interest income recognized on a cash basis for nonaccrual loans	$ 8	$ 37	$ 23
Interest income recognized on accrual method for accruing impaired loans	1,400	1,500	$ 1,800
Reserve for uncollected interest	10	0
Off-balance Sheet Risks, Amount, Liability	$ 385	$ 381