Loans and Leases - Additional Allowance for Credit Losses Relating to Acquired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	$ 6,568	$ 7,268
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	3,734	4,538
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	127	500
Total Commercial Loans and Leases [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	3,861	5,038
Direct Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	994	1,005
Residential Mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	795	632
Indirect Installment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	221	221
Consumer Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total allowance on acquired loans	$ 697	$ 372