Acquisitions and Dispositions - Acquisitions: Purchase Price Allocation (Details) - USD ($)
$ in Thousands
Jul. 07, 2016
Sep. 30, 2016
Dec. 31, 2015
Business Acquisition [Line Items]      
Goodwill   $ 11,180 $ 10,358
The Other Art Fair [Member]      
Business Acquisition [Line Items]      
Goodwill $ 822    
Other assets and liabilities assumed (114)    
Total purchase consideration $ 1,471    
The Other Art Fair [Member] | Weighted Average      
Business Acquisition [Line Items]      
Intangibles, useful life 4 years    
The Other Art Fair [Member] | Trademark      
Business Acquisition [Line Items]      
Intangibles $ 556    
Intangibles, useful life 5 years    
The Other Art Fair [Member] | Artist Relationships      
Business Acquisition [Line Items]      
Intangibles $ 207    
Intangibles, useful life 3 years