Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Securities owned, at fair value:	$ 1,559	$ 2,557
Liabilities
Securities sold, not yet purchased, at fair value:	1	249
Recurring basis
Assets
Total Assets	1,559	2,557
Liabilities
Securities sold, not yet purchased, at fair value:	1
Total Liabilities	1	249
Recurring basis | Corporate stocks-trading securities
Assets
Securities owned, at fair value:	78	244
Liabilities
Securities sold, not yet purchased, at fair value:		249
Recurring basis | Mutual funds
Assets
Securities owned, at fair value:	1,481	2,313
Recurring basis | Level 1
Assets
Total Assets	1,559	2,557
Liabilities
Securities sold, not yet purchased, at fair value:	1
Total Liabilities	1	249
Recurring basis | Level 1 | Corporate stocks-trading securities
Assets
Securities owned, at fair value:	78	244
Liabilities
Securities sold, not yet purchased, at fair value:		249
Recurring basis | Level 1 | Mutual funds
Assets
Securities owned, at fair value:	$ 1,481	$ 2,313