Quarterly report pursuant to Section 13 or 15(d)

Property and Equipment - Schedule Of Interest Expenses For Debt Arrangements (Detail)

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Property and Equipment - Schedule Of Interest Expenses For Debt Arrangements (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Mar. 31, 2017
Property, Plant and Equipment [Line Items]    
Property and equipment, net $ 7,376 $ 7,386
National Holdings [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment 1,364  
Less: accumulated depreciation (134)  
Property and equipment, net 1,230  
Equipment [Member] | National Holdings [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment $ 719  
Property Plant And Equipment Useful Life 5 years  
Furniture And Fixtures [Member] | National Holdings [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment $ 71  
Property Plant And Equipment Useful Life 5 years  
Leaseholds And Leasehold Improvements [Member] | National Holdings [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment $ 298  
Property, Plant and Equipment, Estimated Useful Lives Lesser of useful life or term of lease  
Capital leases (primarily composed of computer equipment) [Member] | National Holdings [Member]    
Property, Plant and Equipment [Line Items]    
Total property and equipment $ 276  
Property Plant And Equipment Useful Life 5 years