| 
           Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) 
        In Thousands, unless otherwise specified  | 
        6 Months Ended | 12 Months Ended | 6 Months Ended | 6 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 
           Jun. 30, 2014
 
          Segment
 
          Unit 
         | 
        
           Dec. 31, 2013
 
          Unit 
         | 
        
           Jun. 30, 2014
 
          Minimum 
         | 
        
           Jun. 30, 2014
 
          Maximum 
         | 
        
           Jun. 30, 2014
 
          Leasehold Improvements 
         | 
        
           Jun. 30, 2014
 
          Other Fixed Assets
 
          Minimum 
         | 
        
           Jun. 30, 2014
 
          Other Fixed Assets
 
          Maximum 
         | 
        
           Jun. 30, 2014
 
          Class A Common Stock 
         | 
        
           Jun. 26, 2013
 
          Class A Common Stock 
         | 
        
           Jun. 30, 2014
 
          Class B Common Stock 
         | 
        
           Jun. 30, 2014
 
          Slp
 
          Class B Common Stock 
         | 
      |
| Summary Of Significant Accounting Policies [Line Items] | |||||||||||
| Ownership percentage in a subsidiary | 62.00% | 62.00% | |||||||||
| Number of operating segment | 1 | ||||||||||
| Cash equivalents, maximum maturity period | 90 days | ||||||||||
| Equity method investments, unrealized intercompany profit (loss) not eliminated amount | $ 0 | ||||||||||
| Property, plant and equipment, useful life | 10 years | 3 years | 7 years | ||||||||
| Number of reporting unit | 1 | 1 | |||||||||
| Identifiable finite-lived intangible assets, useful life | 3 years | 20 years | |||||||||
| Common stock voting rights | 1 vote per share | 1 vote per share | |||||||||
| Class of share exchangeable to another class | one share of Class A common stock | one share of Class A common stock | |||||||||