Description of the Business and Significant Accounting Policies (Details) (USD $)
1 Months Ended 9 Months Ended
Aug. 31, 2012
Jul. 31, 2012
Apr. 30, 2012
Oct. 31, 2012
Jul. 25, 2012
Apr. 24, 2012
Initial Public Offering            
Number of shares sold to public     15,525,000      
Shares of common stock issued pursuant to the full exercise of overallotment option granted to the underwriters     2,025,000      
Common stock sold by selling stockholders (in shares)     992,722      
Aggregate net proceeds received     $ 225,225,000 $ 225,225,000    
Number of shares of common stock issued upon conversion of convertible preferred stock           56,930,194
Number of shares of common stock issuable against warrants           469,557
Shares offered by the stockholders to the public         11,744,064  
Share price of shares offered by the stockholders to the public (in dollars per share)         $ 28.25  
Aggregate offering price for shares sold in the offering, net of underwriting discounts and commissions   $ 320,200,000        
Shares issued pursuant to exercise of underwriters option to purchase additional shares 1,761,609