Loan Servicing - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Transfers And Servicing [Abstract]
Unpaid principal balance of residential mortgage loans serviced for others	$ 1,074,511,000		$ 1,046,551,000
Increased in valuation allowance of mortgage servicing rights	$ 280,000	$ 0

The net increase (decrease) in the valuation allowance for servicing assets subsequently measured using the amortization method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122739-111746

Name:	us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration