Quarterly report pursuant to Section 13 or 15(d)

Debt - Narrative (Details)

v3.21.2
Debt - Narrative (Details) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Dec. 31, 2018
Oct. 29, 2021
Debt Instrument [Line Items]              
Interest expense debt $ 4,242,000 $ 8,139,000 $ 12,682,000 $ 21,907,000      
Interest expense debt excluding amortization 2,479,000 $ 1,951,000 7,439,000 $ 4,962,000      
Convertible Notes due 2023              
Debt Instrument [Line Items]              
Face amount 345,000,000   345,000,000   $ 345,000,000    
Unamortized issuance costs on convertible notes $ 3,491,000   $ 3,491,000   4,306,000    
Issuance costs           $ 10,000,000  
Debt issuance cost           8,600,000  
Convertible debt, carrying amount of equity component, offering costs           $ 1,400,000  
Effective interest rate 2.40% 6.00% 2.40% 6.00%      
Convertible Notes due 2025              
Debt Instrument [Line Items]              
Face amount $ 517,500,000   $ 517,500,000   517,500,000    
Unamortized issuance costs on convertible notes $ 11,376,000   $ 11,376,000   11,731,000    
Issuance costs         14,500,000    
Debt issuance cost         12,600,000    
Convertible debt, carrying amount of equity component, offering costs         $ 1,900,000    
Effective interest rate 1.30% 4.00% 1.30% 4.00%      
Line of Credit | Revolving Credit Facility              
Debt Instrument [Line Items]              
Debt covenant, aggregate investment limit $ 25,000,000   $ 25,000,000        
Current borrowing capacity 500,000,000   500,000,000        
Line of Credit | Revolving Credit Facility | Subsequent Event              
Debt Instrument [Line Items]              
Debt covenant, aggregate investment limit             $ 50,000,000
Convertible Notes Payable              
Debt Instrument [Line Items]              
Interest expense debt 3,700,000 $ 6,500,000 11,100,000 $ 15,000,000      
Interest expense debt excluding amortization 2,500,000 2,000,000 7,400,000 5,000,000      
Amortization of debt discount and issuance costs $ 1,200,000 $ 4,500,000 $ 3,700,000 $ 10,000,000