Regulatory Requirements and Subsidiary Dividend Restrictions - Minimum net capital (Details)	Sep. 30, 2017 USD ($)
Capital and Other Regulatory Requirements [Abstract]
Minimum Net Capital Required for Broker-Dealer Subsidiary	$ 1,000,000
Minimum Net Capital Required for Entity	$ 0.08

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

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