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Debt and Credit Facilities - Additional Information (Details)
 1 Months Ended 3 Months Ended 6 Months Ended 9 Months Ended 12 Months Ended
Jul. 01, 2014
USD ($)
Jul. 31, 2021
USD ($)
Jun. 30, 2021
USD ($)
Extension
Aug. 31, 2020
USD ($)
d
$ / shares
shares
Sep. 30, 2021
USD ($)
$ / shares
Sep. 30, 2020
USD ($)
Jun. 30, 2021
USD ($)
Sep. 30, 2021
USD ($)
d
$ / shares
shares
Sep. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
Mar. 31, 2021
USD ($)
Jan. 01, 2021
USD ($)
Aug. 10, 2020
USD ($)
Debt Instrument [Line Items]                          
Letters of credit outstanding amount         $ 221,200,000     $ 221,200,000   $ 193,100,000      
Proceeds from issuance of warrants               0 $ 13,808,000        
Deferred tax liabilities         23,554,000     23,554,000   12,285,000      
Deferred tax assets         147,260,000     147,260,000   130,200,000      
Level 2                          
Debt Instrument [Line Items]                          
Senior notes, fair value         223,100,000     223,100,000          
Senior Notes                          
Debt Instrument [Line Items]                          
Debt instrument, outstanding amount         200,000,000     200,000,000   200,000,000      
Senior Note, Series A                          
Debt Instrument [Line Items]                          
Senior note, amount paid   $ 50,000,000                      
Convertible Senior Notes                          
Debt Instrument [Line Items]                          
Interest rate       0.25%                  
Interest expense         700,000 $ 1,600,000   $ 2,200,000 1,600,000 4,400,000      
Debt amount       $ 400,000,000.0                  
Exercise of option by initial purchasers aggregate principal amount       50,000,000.0                  
Proceeds from issuance and sale of debt       389,700,000                  
Transaction fees and other third-party offering expenses       $ 10,300,000                  
Debt instrument, payment terms               The Convertible Senior Notes accrue interest at a rate of 0.25% per annum, payable semi-annually on February 15 and August 15 of each year beginning on February 15, 2021          
Debt instrument, frequency of periodic payment               semi-annually          
Maturity Date       Aug. 15, 2025                  
Convertible note converted each amount         $ 1,000     $ 1,000          
Convertible notes converted each into shares of common stock | shares               22.2913          
Debt Instrument, conversion price | $ / shares         $ 44.86     $ 44.86          
Threshold trading days | d       20       51          
Threshold consecutive trading days | d       30                  
Conversion percentage of stock price trigger       130.00%                  
Number of business day period       5 days                  
Consecutive trading day period       5 days                  
Convertible principal amount       $ 1,000                  
Measurement period, percentage       98.00%                  
Percentage of principal amount to redeem convertible senior notes       100.00%                  
Percentage of convertible senior notes repurchased at cash       100.00%                  
Debt liability       $ 336,100,000                  
Debt instrument convertible notes additional paid in capital       $ 53,600,000                  
Convertible senior notes effective interest rate       3.25%                  
Net carrying value of notes         $ 400,000,000.0     $ 400,000,000.0   340,600,000      
Bond hedge term               5 years          
Number of shares issuable upon conversion | shares       8,900,000                  
Cost of convertible note hedge transaction       $ 55,000,000.0                  
Number of common stock acquired by offsetting sale warrants. | shares               8,900,000          
Exercise price of warrants | $ / shares         $ 66.46     $ 66.46          
Proceeds from issuance of warrants               $ 13,800,000          
Convertible Senior Notes | ASU 2020-06                          
Debt Instrument [Line Items]                          
Reclassification of equity component of convertible senior notes to liabilities                     $ 55,000,000.0    
Reclassification of equity component of debt issuance costs to liabilities                     $ 1,400,000    
Carrying amount of convertible senior notes adjusted in retained earnings                       $ 3,700,000  
Convertible Note Hedge And Warrant Transaction                          
Debt Instrument [Line Items]                          
Purchase of bond hedges and sale of warrants       $ 41,200,000                  
Deferred tax liabilities         $ 16,200,000     16,200,000          
Deferred tax assets         16,500,000     16,500,000          
Convertible Note Hedge And Warrant Transaction | ASU 2020-06                          
Debt Instrument [Line Items]                          
Deferred tax liability reversed         13,900,000     13,900,000          
Additional deferred tax liability related to capitalized debt issuance costs         400,000     400,000          
Adjustment to deferred tax asset through retained earnings         900,000     900,000          
Private Placement                          
Debt Instrument [Line Items]                          
Debt issuance costs incurred $ 1,100,000                       $ 500,000
Debt amount 250,000,000.0                        
Private Placement | Accrued Expenses and Other Current Liabilities                          
Debt Instrument [Line Items]                          
Interest payable         2,000,000.0     2,000,000.0   $ 5,500,000      
Private Placement | Senior Notes                          
Debt Instrument [Line Items]                          
Interest expense         2,700,000 3,100,000   8,900,000 9,300,000        
Interest payments         $ 6,200,000 6,200,000   $ 12,400,000 12,400,000        
Private Placement | Senior Note, Series A                          
Debt Instrument [Line Items]                          
Debt amount $ 50,000,000                        
Maturity Date Jul. 15, 2021                        
Minimum | Convertible Senior Notes                          
Debt Instrument [Line Items]                          
Debt Instrument, conversion price | $ / shares       $ 44.86                  
Percentage of bond hedge and warrant transactions increased conversion price       35.00%                  
Maximum | Convertible Senior Notes                          
Debt Instrument [Line Items]                          
Debt Instrument, conversion price | $ / shares       $ 66.46                  
Percentage of bond hedge and warrant transactions increased conversion price       100.00%                  
Unsecured Revolving Credit Facility                          
Debt Instrument [Line Items]                          
Credit agreement date     Jun. 30, 2021                    
Revolving credit facility     $ 650,000,000       $ 650,000,000            
Debt issuance costs incurred     1,900,000       1,900,000            
Revolving credit facility     $ 550,000,000       $ 550,000,000            
Credit agreement maturity period     5 years                    
Credit agreement number of extensions | Extension     2                    
Interest rate         1.34%     1.34%   1.87%      
Letters of credit outstanding amount         $ 45,000,000.0     $ 45,000,000.0   $ 44,900,000      
Interest expense         100,000 $ 200,000   600,000 $ 900,000        
Debt instrument, outstanding amount         $ 0     $ 0          
Unsecured Revolving Credit Facility | Base Rate | Minimum                          
Debt Instrument [Line Items]                          
Margin interest rate             0.00%            
Unsecured Revolving Credit Facility | Base Rate | Maximum                          
Debt Instrument [Line Items]                          
Margin interest rate             0.625%            
Unsecured Revolving Credit Facility | Euro Currency Rate | Minimum                          
Debt Instrument [Line Items]                          
Margin interest rate             1.00%            
Unsecured Revolving Credit Facility | Euro Currency Rate | Maximum                          
Debt Instrument [Line Items]                          
Margin interest rate             1.625%