Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
Securities owned, at fair value:	$ 1,256	$ 1,559
Liabilities
Securities sold, not yet purchased, at fair value:		1
Recurring basis
Assets
Total Assets	1,256	1,559
Liabilities
Total Liabilities		1
Recurring basis | Corporate stocks-trading securities
Assets
Securities owned, at fair value:	14	78
Liabilities
Securities sold, not yet purchased, at fair value:		1
Recurring basis | Mutual funds
Assets
Securities owned, at fair value:	1,242	1,481
Recurring basis | Level 1
Assets
Total Assets	1,256	1,559
Liabilities
Total Liabilities		1
Recurring basis | Level 1 | Corporate stocks-trading securities
Assets
Securities owned, at fair value:	14	78
Liabilities
Securities sold, not yet purchased, at fair value:		1
Recurring basis | Level 1 | Mutual funds
Assets
Securities owned, at fair value:	$ 1,242	$ 1,481