Quarterly report pursuant to sections 13 or 15(d)

Stockholders' Equity - Summary of Authorized and Outstanding Equity (Parenthetical) (Detail)

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Stockholders' Equity - Summary of Authorized and Outstanding Equity (Parenthetical) (Detail) (USD $)
6 Months Ended
Jun. 30, 2013
Schedule Of Stockholders Equity [Line Items]  
Preferred stock, par value $ 0.01
Class A Common Stock [Member]
 
Schedule Of Stockholders Equity [Line Items]  
Common stock, par value $ 0.01
Common stock voting rights 1 vote per share
Common stockholders rights percentage 100.00%
Common stock, shares outstanding 4,790,694
Class B Common Stock [Member]
 
Schedule Of Stockholders Equity [Line Items]  
Common stock, par value $ 0.01
Common stock voting rights 1 vote per share
Class of share exchangeable to another class One share of Class A common stock
Common stock, shares outstanding 6,459,316
Deferred equity units exercisable 191,828