Notes Payable - Components of Notes Payable (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total	$ 30,573	$ 26,417
Unamortized discount	647	872
Notes payable to KMS' former shareholders, net of $159 and $221 of unamortized discount in 2017 and 2016, respectively
Debt Instrument [Line Items]
Unamortized discount	159	221
Notes payable to SSN's former shareholders, net of $488 and $651 of unamortized discount in 2017 and 2016, respectively
Debt Instrument [Line Items]
Unamortized discount	488	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	7,815	153
Notes Payable \| Note payable under subsidiary's revolver with bank
Debt Instrument [Line Items]
Long-term debt	392	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 $159 and $221 of unamortized discount in 2017 and 2016, respectively
Debt Instrument [Line Items]
Long-term debt	2,910	3,852
Notes Payable \| Notes payable to SSN's former shareholders, net of $488 and $651 of unamortized discount in 2017 and 2016, respectively
Debt Instrument [Line Items]
Long-term debt	$ 8,433	$ 10,769