Notes Payable - Components of Notes Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total	$ 28,182	$ 26,417
Unamortized discount	535	872
Notes payable to KMS' former shareholders, net of $128 and $221 of unamortized discount in 2017 and 2016, respectively
Debt Instrument [Line Items]
Unamortized discount	128	221
Notes payable to SSN's former shareholders, net of $407 and $651 of unamortized discount in 2017 and 2016, respectively
Debt Instrument [Line Items]
Unamortized discount	407	651
Notes Payable \| Notes payable to clearing firm under forgivable loans
Debt Instrument [Line Items]
Long-term debt	4,285	4,285
Notes Payable \| Note payable under subsidiary's term loan with bank
Debt Instrument [Line Items]
Long-term debt	7,192	153
Notes Payable \| Note payable under subsidiary's revolver with bank
Debt Instrument [Line Items]
Long-term debt	276	620
Notes Payable \| Notes payable by subsidiary to certain former shareholders of Highland
Debt Instrument [Line Items]
Long-term debt	6,738	6,738
Notes Payable \| Notes payable to KMS' former shareholders, net of $128 and $221 of unamortized discount in 2017 and 2016, respectively
Debt Instrument [Line Items]
Long-term debt	2,435	3,852
Notes Payable \| Notes payable to SSN's former shareholders, net of $407 and $651 of unamortized discount in 2017 and 2016, respectively
Debt Instrument [Line Items]
Long-term debt	$ 7,256	$ 10,769