Restriction on Cash and Due From Banks - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Cash Reserve Deposit Required and Made	$ 3.7	$ 4.0

Cash deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 305
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6478312&loc=d3e61473-112792

Name:	us-gaap_CashReserveDepositRequiredAndMade
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant