Capital and Reserve Requirement Information - Summary of Aggregate Indebtedness, Net Capital and Resultant Ratio for VPD (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Brokers and Dealers [Abstract]
Aggregate indebtedness	$ 23,511us-gaap_AggregateIndebtedness	$ 28,020us-gaap_AggregateIndebtedness	$ 23,443us-gaap_AggregateIndebtedness
Net capital	$ 21,919us-gaap_NetCapital	$ 22,086us-gaap_NetCapital	$ 16,617us-gaap_NetCapital
Ratio of aggregate indebtedness to net capital	1.1	1.3	1.4

Net capital is equal to the net worth of the broker dealer, less certain items such as exchange memberships, carrying value of securities not readily marketable, haircuts on marketable securities in proprietary accounts, furniture and equipment and other illiquid assets as defined.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Rule 15c3

-Number 240

-Section 1

-Paragraph 1

-Subparagraph ii

-Article 15c3

-Subsection a

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