Fair Value Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Assets
Securities owned, at fair value:	$ 1,923	$ 2,557
Liabilities
Securities sold, not yet purchased, at fair value:		249
Recurring basis
Assets
Total Assets	1,924	2,557
Liabilities
Total Liabilities		249
Recurring basis | Money market mutual funds
Assets
Cash and cash equivalents:	1
Recurring basis | Corporate stocks-trading securities
Assets
Securities owned, at fair value:		244
Liabilities
Securities sold, not yet purchased, at fair value:		249
Recurring basis | Mutual funds
Assets
Securities owned, at fair value:	1,923	2,313
Recurring basis | Level 1
Assets
Total Assets	1,924	2,557
Liabilities
Total Liabilities		249
Recurring basis | Level 1 | Money market mutual funds
Assets
Cash and cash equivalents:	1
Recurring basis | Level 1 | Corporate stocks-trading securities
Assets
Securities owned, at fair value:		244
Liabilities
Securities sold, not yet purchased, at fair value:		249
Recurring basis | Level 1 | Mutual funds
Assets
Securities owned, at fair value:	$ 1,923	$ 2,313