Loans and Allowance for Loan Losses - Recorded Investment in Impaired Loans and Related Valuation Allowance (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Receivables [Abstract]
Recorded Investment	$ 28,080	$ 27,371	$ 27,175
Valuation Allowance	$ 5,072	$ 5,012	$ 5,262

Amount of allowance for credit losses related to recorded investment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524

Name:	us-gaap_ImpairedFinancingReceivableRelatedAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant