Annual report pursuant to Section 13 and 15(d)

Debt (Credit Agreement) (Details)

v3.20.4
Debt (Credit Agreement) (Details) - USD ($)
 12 Months Ended
Nov. 19, 2015
Dec. 31, 2020
Jul. 31, 2017
Second Amended and Restated Credit Agreement      
Line of Credit Facility [Line Items]      
Credit facility amount     $ 500,000,000
Right to increase credit facility, amount     150,000,000
Credit facility outstanding   $ 0  
Letters of credit      
Line of Credit Facility [Line Items]      
Credit facility amount     $ 5,000,000
Credit Agreement      
Line of Credit Facility [Line Items]      
Voting equity of foreign subsidiary pledged 66.00%    
Non-voting equity of foreign subsidiary pledged 100.00%    
Commitment fee   0.25%  
Credit Agreement | Prepaid Expenses      
Line of Credit Facility [Line Items]      
Debt issuance cost, outstanding   $ 853,000  
Credit Agreement | Other non-current assets      
Line of Credit Facility [Line Items]      
Debt issuance cost, outstanding   $ 2,337,000  
Credit Agreement | Minimum | LIBOR      
Line of Credit Facility [Line Items]      
Spread on variable rate basis 1.50%    
Credit Agreement | Maximum | LIBOR      
Line of Credit Facility [Line Items]      
Spread on variable rate basis 3.25%