Quarterly report pursuant to Section 13 or 15(d)

Description of Business and Basis of Presentation (Details)

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Description of Business and Basis of Presentation (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
 1 Months Ended 9 Months Ended
Sep. 30, 2013
Oct. 31, 2013
Follow-on Public Offering    
Number of shares of common stock issued 15,730,000  
Number of shares of common stock sold pursuant to the exercise by the underwriters of an option to purchase additional shares 2,730,000  
Public offering price (in dollars per share) $ 25.00  
Number of shares sold by selling shareholder 5,200,000  
Aggregate net proceeds after deducting underwriting discounts and commissions and offering expenses $ 379,100 $ 379,088
Fiscal Year    
Current fiscal year end date   --12-31
Fourth fiscal quarter transition period   2 months
Current fiscal year transition period   11 months