Annual report pursuant to Section 13 and 15(d)

Acquisitions (Purchase Price Allocation) (Details)

v3.8.0.1
Acquisitions (Purchase Price Allocation) (Details) - USD ($)
$ in Thousands
Jan. 02, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Business Acquisition [Line Items]        
Goodwill   $ 124,210 $ 124,031 $ 125,572
SSN        
Business Acquisition [Line Items]        
Cash $ 8,081      
Securities owned, at fair value 158      
Receivables from clearing broker 630      
Other receivables, net 11,711      
Fixed assets, net 57      
Restricted assets 225      
Identifiable intangible assets 30,901      
Goodwill 9,282      
Other assets 714      
Total assets acquired 61,759      
Commissions and fees payable (12,562)      
Deferred income (44)      
Accounts payable and accrued liabilities (1,866)      
Total liabilities assumed (14,472)      
Total estimated purchase price 47,287      
SSN | Other Receivables, Net and Commissions and Fees Payable        
Business Acquisition [Line Items]        
Increase in original amount 484      
SSN | Goodwill and Accounts Payable and Accrued Liabilities        
Business Acquisition [Line Items]        
Increase in original amount $ 9,100