Allowance for Loan Losses - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Category	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Loans and Leases Receivable Disclosure [Line Items]
Number of categories occupied under commercial real estate loans | Category	2
Originated Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Impaired TDRs Loans	$ 12,371,000	$ 29,269,000	$ 45,676,000
Additional funds in TDRs	25,000	35,000	54,000
PNCI Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Impaired TDRs Loans	1,324,000	1,396,000	1,307,000
Obligations to lend additional funds on TDRs	$ 0	$ 0	$ 0
Minimum [Member]
Loans and Leases Receivable Disclosure [Line Items]
Period of collateral payment of loan	3 months
Maximum [Member]
Loans and Leases Receivable Disclosure [Line Items]
Period of collateral payment of loan	12 months