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Convertible Senior Notes - Narrative (Details)
$ / shares in Units, shares in Millions
1 Months Ended 3 Months Ended 12 Months Ended
Dec. 31, 2019
Jun. 30, 2019
USD ($)
day
$ / shares
Feb. 28, 2018
USD ($)
day
$ / shares
shares
Mar. 31, 2020
$ / shares
Dec. 31, 2019
Debt Instrument [Line Items]          
Total cost of bond hedge     $ 41,700,000    
Number of warrants issued, subject to anti-dilution adjustments (in shares) | shares     4.0    
Warrant strike price (usd per share) | $ / shares     $ 78.75    
Proceeds from warrants     $ 22,400,000    
Convertible Senior Notes Due February 2023 | Convertible Debt          
Debt Instrument [Line Items]          
Interest rate     0.75%    
Principal amount     $ 230,000,000.0    
Initial conversion rate of common stock     0.0174292    
Conversion price (usd per share) | $ / shares     $ 57.38    
Limitation on sale of common stock, sale price threshold, number of trading days | day     20    
Limitation on sale of common stock, sale price threshold, trading period | day     30    
Threshold percentage of stock price trigger 130.00%   130.00%    
Number of consecutive business days       5 days  
Percentage of closing sale price in excess of convertible notes         98.00%
Redemption price percentage     100.00%    
Effective interest rate of liability component     5.875%    
Issuance costs attributable to the liability component     $ 5,300,000    
Net issuance costs related to the equity component     $ 1,500,000    
Remaining amortization period for debt discount and debt issuance costs       2 years 10 months 24 days  
Number of securities called by bond hedge (in shares) | shares     0.9    
Convertible Senior Notes Due June 2026 | Convertible Debt          
Debt Instrument [Line Items]          
Interest rate   0.75%      
Principal amount   $ 316,300,000      
Initial conversion rate of common stock       0.0112851  
Conversion price (usd per share) | $ / shares   $ 88.61   $ 88.61  
Limitation on sale of common stock, sale price threshold, number of trading days | day   20      
Limitation on sale of common stock, sale price threshold, trading period | day   30      
Threshold percentage of stock price trigger   130.00%      
Number of consecutive business days       5 days  
Percentage of closing sale price in excess of convertible notes   98.00%      
Redemption price percentage   100.00%      
Effective interest rate of liability component       5.38%  
Issuance costs attributable to the liability component   $ 6,400,000      
Net issuance costs related to the equity component   $ 2,900,000      
Remaining amortization period for debt discount and debt issuance costs       6 years 3 months 18 days  
Initial strike price (in usd per share) | $ / shares       $ 88.6124  
Initial cap price (in usd per share) | $ / shares   $ 139.00   $ 139.00  
Cost incurred in connection with capped calls   $ 40,800,000