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Common and Capital Stock Reserved for Future Issuance (Detail) - shares
Dec. 31, 2016
Dec. 31, 2015
Class of Stock [Line Items]    
Total 42,513,729 36,637,349
Class B Common Stock    
Class of Stock [Line Items]    
Shares issuable upon conversion of outstanding Class B common stock 6,217,447 6,217,447
Option Awards    
Class of Stock [Line Items]    
Option awards outstanding 29,628,443 27,126,374
Option Awards | 2011 Plan    
Class of Stock [Line Items]    
Class A common stock and Class C capital stock available for grant under 2011 Plan 2,887,262 688,014
Restricted Stock Units    
Class of Stock [Line Items]    
Restricted stock units outstanding 3,780,577 2,605,514