Income Taxes (Details 3) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Share-based compensation expense	$ 3,851,000	$ 6,325,000
Deferred rent	441,000	762,000
Compensation and benefits payable	719,000	4,907,000
Federal unrecognized tax benefit	46,000	942,000
Other	140,000	74,000
Total deferred tax assets	5,197,000	13,010,000
Deferred tax liabilities:
Property and equipment	(586,000)	(1,013,000)
Intangibles	(1,029,000)	(1,023,000)
Unrealized gains on investments	(175,000)	(71,000)
Total deferred tax liabilities	(1,790,000)	(2,107,000)
Net deferred tax assets	$ 3,407,000	$ 10,903,000