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Debt- Narrative (Details)
$ / shares in Units, shares in Millions
1 Months Ended 9 Months Ended
Sep. 04, 2020
USD ($)
Sep. 30, 2020
USD ($)
trading_day
$ / shares
Oct. 31, 2020
USD ($)
$ / shares
shares
Oct. 31, 2019
USD ($)
Jan. 31, 2020
USD ($)
Debt Instrument [Line Items]          
Liability component issuance costs   $ 13,200,000      
Equity component issuance costs   $ 3,600,000 $ 3,600,000    
Indexed shares | shares     14.6    
Purchase of capped calls related to convertible senior notes     $ 61,870,000 $ 0  
Capped call          
Debt Instrument [Line Items]          
Initial strike price (in dollars per share) | $ / shares     $ 39.35    
Option cap price (in dollars per share) | $ / shares     $ 58.30    
Purchase of capped calls related to convertible senior notes     $ 61,900,000    
Revolving Credit Facility          
Debt Instrument [Line Items]          
Maximum borrowing capacity $ 50,000,000.0   50,000,000.0   $ 50,000,000.0
Amount of right to add revolving commitments $ 50,000,000.0        
Commitment fee percentage 0.25%        
Current borrowing capacity     50,000,000.0    
Revolving Credit Facility | LIBOR          
Debt Instrument [Line Items]          
Variable interest rate 1.75%        
Revolving Credit Facility | Base Rate          
Debt Instrument [Line Items]          
Variable interest rate 0.75%        
Standby Letters of Credit          
Debt Instrument [Line Items]          
Maximum borrowing capacity $ 40,000,000.0        
Standby Letters of Credit | Office Lease Facilities          
Debt Instrument [Line Items]          
Standby letters of credit     4,500,000    
Senior Convertible Debt          
Debt Instrument [Line Items]          
Stated interest rate   0.125%      
Principal amount of debt   $ 575,000,000.0      
Initial conversion ratio   25.4113      
Initial conversion price (in dollars per share) | $ / shares   $ 39.35      
Carrying amount of equity component     $ 122,500,000    
Effective interest rate     5.00%    
Senior Convertible Debt | Additional Paid-In Capital          
Debt Instrument [Line Items]          
Carrying amount of equity component     $ 118,700,000    
Senior Convertible Debt | Debt Instrument, Redemption, Period One          
Debt Instrument [Line Items]          
Threshold scheduled trading days | trading_day   41      
Threshold trading days | trading_day   20      
Threshold consecutive trading days | trading_day   30      
Senior Convertible Debt | Minimum | Debt Instrument, Redemption, Period One          
Debt Instrument [Line Items]          
Redemption price percentage   100.00%      
Senior Convertible Debt | Minimum | Debt Instrument, Redemption, Period Two          
Debt Instrument [Line Items]          
Threshold percentage of stock price trigger   98.00%      
Threshold trading days | trading_day   5      
Threshold consecutive trading days | trading_day   5      
Senior Convertible Debt | Maximum | Debt Instrument, Redemption, Period One          
Debt Instrument [Line Items]          
Threshold percentage of stock price trigger   130.00%      
Senior Convertible Debt | Maximum | Debt Instrument, Redemption, Period Two          
Debt Instrument [Line Items]          
Threshold percentage of stock price trigger   130.00%      
Threshold trading days | trading_day   20      
Threshold consecutive trading days | trading_day   30