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Convertible Senior Notes - Narrative (Details) - Convertible Debt - Convertible Senior Notes Due 2024
1 Months Ended 6 Months Ended
Mar. 08, 2017
Mar. 31, 2017
USD ($)
$ / shares
Dec. 30, 2017
USD ($)
d
Jul. 01, 2017
USD ($)
Debt Instrument [Line Items]        
Debt, aggregate principal amount   $ 450,000,000 $ 450,000,000 $ 450,000,000
Debt, stated interest rate   0.25%    
Conversion rate 0.0164965      
Conversion price (usd per share) | $ / shares   $ 60.62    
Conversion price premium percentage   132.50%    
Conversion threshold trading days | d     20  
Conversion threshold consecutive trading days | d     30  
Conversion threshold percentage of stock price trigger     130.00%  
Conversion threshold measurement period     5 days  
Conversion threshold percentage of conversion rate from measurement period     98.00%  
Percentage of principal amount required to be paid upon contingent note repurchase     100.00%  
Derivative liability fair value   $ 129,900,000    
Residual principal amount of notes before issuance costs   320,100,000    
Debt issuance costs   $ 7,700,000    
Effective interest rate on the liability component   5.40% 5.40%  
Debt, remaining discount amortization period     74 months