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Convertible Senior Notes - Additional Information (Detail)
$ / shares in Units, shares in Millions
12 Months Ended
May 02, 2017
USD ($)
d
$ / shares
shares
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Debt Instrument [Line Items]        
Convertible senior notes principal amount   $ 517,500,000 $ 517,500,000  
Proceeds from Senior Convertible Notes   $ 0 0 $ 502,781,000
2.25% Convertible Senior Notes due 2024        
Debt Instrument [Line Items]        
Convertible senior notes principal amount $ 517,500,000      
Convertible senior notes interest percentage 2.25%      
Convertible senior notes convertible latest date May 15, 2024      
Proceeds from Senior Convertible Notes $ 502,800,000      
Threshold common stock trading days | d 20      
Threshold consecutive common stock trading days | d 30      
Threshold percentage of common stock price trigger 130.00%      
Debt instrument conversion obligation number of consecutive business days after consecutive trading day period 5 days      
Principal amount on conversion rate $ 1,000      
Minimum percentage of common stock price trigger 98.00%      
Debt instrument convertible trading days during observation period 30 days      
Conversion Observation Period 25 days      
Debt instrument conversion value description The conversion value is the sum of the daily conversion value which is the product of the effective conversion rate divided by 25 days and the daily VWAP of our common stock.      
Debt instrument conversion share amount description The “share amount” is the cumulative “daily share amount” during the observation period, which is calculated by dividing the daily VWAP into the difference between the daily conversion value (i.e., conversion rate x daily VWAP) and $1,000.      
Convertible senior notes convertible in to shares 0.00131711      
Convertible senior notes conversion price | $ / shares $ 75.92      
Shares issued to settle notes at initial conversion rate | shares 6.8      
Market Price of Common stock | $ / shares $ 53.28      
Convertible senior note premium 42.50%      
Convertible senior notes redemption rate 100.00%      
Convertible senior note carrying value of the liability component $ 368,300,000      
Convertible senior note assumed borrowing rate 7.50%      
Convertible senior note carrying value of the equity component $ 149,200,000      
Convertible senior notes term 7 years      
Discount on liability component, remaining amortization period   4 years 4 months 24 days    
Transaction cost related to issuance of convertible senior note $ 14,700,000      
Debt instrument events of default percentage of principal and accrued and unpaid interest due and payable upon default 100.00%      
Convertible senior notes fair value   $ 596,800,000 $ 616,100,000