RCap Regulatory Requirements - Additional Information (Detail)	Sep. 30, 2016 USD ($)
Regulatory Capital Requirements [Abstract]
Minimum net capital requirement	$ 300,000
Regulatory net capital	391,200,000
Regulatory net capital, excess net capital	$ 390,900,000

Minimum amount of net capital required to be maintained by entity's broker-dealer subsidiary to engage in securities transactions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

Name:	us-gaap_MinimumNetCapitalRequiredForBrokerDealerSubsidiary1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant