Common Stock-Narrative (Details)
12 Months Ended
Dec. 31, 2015
class_of_stock
$ / shares
shares
Aug. 16, 2014
shares
Class of Stock [Line Items]    
Number of classes of common stock (class of stock) | class_of_stock 2  
Class A Common Stock    
Class of Stock [Line Items]    
Approval rate to waive equal consideration rights (ratio) 75.00%  
Shares repurchased (in shares) 517,700  
Average cost (usd per share) | $ / shares $ 6.62  
Class B Common Stock    
Class of Stock [Line Items]    
Shares repurchased (in shares) 0  
2014 Repurchase Authorization    
Class of Stock [Line Items]    
Remaining number of shares authorized to be repurchased 1,455,300  
2014 Repurchase Authorization | Common Stock    
Class of Stock [Line Items]    
Number of shares authorized to be repurchased   2,000,000