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Debt - Narrative (Details)
$ / shares in Units, shares in Millions
1 Months Ended 9 Months Ended
May 31, 2020
USD ($)
$ / shares
Sep. 30, 2020
USD ($)
day
$ / shares
shares
Sep. 30, 2019
USD ($)
Debt Instrument [Line Items]      
Gross proceeds from issuance of convertible senior notes $ 562,500,000 $ 575,000,000 $ 0
Convertible debt, conversion ratio   0.0267187  
Conversion price (in dollars per share) | $ / shares   $ 37.43  
Convertible debt, equity component $ 205,300,000 $ 200,812,000  
Issuance cost, equity component   $ 0 $ 3,734,000
Closing share price (in dollars per share) | $ / shares   $ 41.06  
If-converted value in excess of principal   $ 56,000,000  
Remaining life, convertible debt   56 months  
Shares covered by capped calls (in shares) | shares   15.4  
Purchases of capped calls related to convertible senior notes   $ 67,333,000  
Class A common stock      
Debt Instrument [Line Items]      
Capped call, initial strike price (in dollars per share) | $ / shares $ 37.43    
Capped call, initial cap price (in dollars per share) | $ / shares $ 57.58    
Convertible senior notes      
Debt Instrument [Line Items]      
Debt principal amount $ 575,000,000.0    
Face amount, additional principal issuable $ 75,000,000.0    
Interest rate 0.75% 0.75%  
Issuance cost, liability component $ 8,000,000.0    
Issuance cost, equity component $ 4,500,000    
Measurement Input, Effective Interest Rate | Convertible senior notes      
Debt Instrument [Line Items]      
Measurement input   0.100  
Scenario One, Prior to February 14, 2025      
Debt Instrument [Line Items]      
Conversion requirement, threshold trading days | day   20  
Conversion requirement, threshold consecutive trading days | day   30  
Conversion requirement, threshold percentage of stock price trigger   130.00%  
Scenario Two, Prior to February 14, 2025      
Debt Instrument [Line Items]      
Conversion requirement, threshold consecutive trading days | day   5  
Conversion requirement, threshold percentage of stock price trigger   98.00%  
Conversion requirement, threshold business days following consecutive trading days | day   5  
Scenario Three, Subsequent to May 20, 2023      
Debt Instrument [Line Items]      
Conversion requirement, threshold trading days | day   20  
Conversion requirement, threshold consecutive trading days | day   30  
Scenario Three, Subsequent to May 20, 2023 | Convertible senior notes      
Debt Instrument [Line Items]      
Conversion requirement, threshold percentage of stock price trigger   130.00%  
Redemption price, percentage   100.00%  
Scenario Four, Fundamental Change | Convertible senior notes      
Debt Instrument [Line Items]      
Redemption price, percentage   100.00%