Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation and Employee Benefit Plans - Additional Information (Detail)

v2.4.0.6
Stock-Based Compensation and Employee Benefit Plans - Additional Information (Detail) (USD $)
3 Months Ended 3 Months Ended 3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2012
Mar. 31, 2013
Class A Common Stock [Member]
vote
Dec. 31, 2012
Class A Common Stock [Member]
Mar. 31, 2013
Class B Common Stock [Member]
vote
Dec. 31, 2012
Class B Common Stock [Member]
Dec. 31, 2012
Equity Incentive Plan [Member]
Mar. 31, 2013
Employee Stock Purchase Plan [Member]
Jan. 02, 2013
Employee Stock Purchase Plan [Member]
Mar. 31, 2013
Restricted Stock Units [Member]
Mar. 31, 2012
Restricted Stock Units [Member]
Mar. 31, 2013
Restricted Stock Awards [Member]
Mar. 31, 2012
Restricted Stock Awards [Member]
Mar. 31, 2013
Stock Options [Member]
Mar. 31, 2012
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Weighted-average grant date fair value per share (usd per share)                     $ 5.46 $ 5.51 $ 0.00 $ 0 $ 0 $ 0
Restricted stock awards granted (shares)                         0 0    
Stock options granted (shares) 0 0                            
Percentage of fair value market of common stock 100.00%                              
Vesting period for new restricted stock units 4 years                              
Term of option granted, minimum 7 years                              
Term of option granted, maximum 10 years                              
Shares authorized for issuance               1,300,000   400,000            
Contribution of earnings by employees                 15.00%              
Percentage of purchase of common stock                 85.00%              
Percentage of common stock on the date of purchase                 85.00%              
Common stock, shares authorized (shares) 550,000,000   550,000,000 500,000,000 500,000,000 500,000,000 500,000,000                  
Voting rights per share       1   10                    
Number of convertible common stock       1