Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation and Summary of Significant Accounting Policies - Derivatives (Details)

v3.10.0.1
Basis of Presentation and Summary of Significant Accounting Policies - Derivatives (Details) - Convertible Notes - USD ($)
Jun. 30, 2018
Jun. 19, 2018
May 22, 2018
Sep. 30, 2018
Dec. 31, 2017
Aug. 31, 2014
2023 Convertible Senior Notes            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Aggregate principal amount outstanding     $ 750,000,000 $ 750,000,000 $ 0  
Interest rate (as a percent)     0.75%      
Common stock price (USD per share)   $ 195.91 $ 187.09      
Exercise price, conversion premium and bond hedge (USD per share)   248.48 248.48      
Exercise price, warrant (USD per share)   $ 315.38 $ 315.38      
Risk-free interest rate (as a percent)   2.80% 2.90%      
Dividend yield (as a percent)   0.00% 0.00%      
Annual coupon rate (as a percent)   0.75% 0.75%      
Remaining contractual term (in years)   4 years 11 months 23 days 5 years      
2023 Convertible Senior Notes | Minimum            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Volatility (as a percent)   30.00% 30.00%      
2023 Convertible Senior Notes | Maximum            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Volatility (as a percent)   35.00% 35.00%      
2019 Convertible Senior Notes            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Aggregate principal amount outstanding       $ 223,215,000 $ 245,000,000 $ 245,000,000.0
Interest rate (as a percent)           0.75%
Common stock price (USD per share)     $ 187.09 $ 274.49    
Exercise price, conversion premium and bond hedge (USD per share)     $ 75.05 $ 75.05   $ 75.05
Risk-free interest rate (as a percent) 2.59%   2.47%      
Dividend yield (as a percent) 0.00%   0.00%      
Annual coupon rate (as a percent) 0.75%   0.75%      
Remaining contractual term (in years) 10 months 20 days   1 year 3 months      
2019 Convertible Senior Notes | Minimum            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Volatility (as a percent) 30.00%   30.00%      
2019 Convertible Senior Notes | Maximum            
Derivative Instruments and Hedging Activities Disclosures [Line Items]            
Volatility (as a percent) 35.00%   35.00%