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Convertible Senior Notes - Narrative (Details) - Convertible debt - 3.00% Convertible senior notes due 2022
 1 Months Ended 9 Months Ended
Aug. 31, 2015
USD ($)
item
$ / shares
Sep. 30, 2016
USD ($)
Dec. 31, 2015
USD ($)
Long-term debt      
Debt principal amount $ 150,000,000.0 $ 150,000,000 $ 150,000,000
Interest rate 3.00%    
Net proceeds from issuance of convertible notes $ 145,400,000    
Trading days, number | item 20    
Consecutive trading days, period 30 days    
Stock price trigger (as a percent) 130.00%    
Business days, period 5 days    
Consecutive trading-day period 5 days    
Common stock per principal amount $ 1,000    
Maximum product of the closing sale price of shares of the Company's common stock and the applicable conversion rate for such trading day (as a percent) 98.00%    
Conversion ratio 17.7487    
Conversion price per share | $ / shares $ 56.34    
Convertible instruments principal and unpaid interest payable upon events of default 100.00%    
Minimum percentage of principal held by convertible debt instrument holders required to issue notice for declaration of principal and unpaid interest payable upon events of default (as a percent) 25.00%    
Term of the convertible notes 7 years    
Net deferred tax liability in connection with convertible notes $ 22,300,000    
Fair value of convertible notes   $ 89,200,000  
Remaining contractual life of the convertible notes   5 years 10 months 24 days  
Redemption on or after August 20, 2018      
Long-term debt      
Trading days, number | item 19    
Consecutive trading days, period 30 days    
Stock price trigger (as a percent) 130.00%    
Redemption price (as a percent) 100.00%    
Sinking fund $ 0