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Short-Term Borrowings and Long-Term Debt - Interest Expense and Senior Notes (Details) - USD ($)
1 Months Ended 12 Months Ended
Dec. 20, 2019
Jan. 31, 2015
Sep. 30, 2010
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Debt Disclosure [Abstract]            
Interest expense on debt       $ 35,100,000 $ 46,600,000 $ 36,100,000
Weighted average interest rate on short-term borrowings         2.62%  
Debt Instrument [Line Items]            
Long-term debt       347,987,000 $ 696,465,000  
3.50% Senior Notes            
Debt Instrument [Line Items]            
Principal value   $ 350,000,000        
Proceeds from issuance of senior notes, net of discount and issuance cost   $ 346,400,000        
Debt issuance costs       1,800,000    
Discount on debt       200,000    
5.375% Senior Notes            
Debt Instrument [Line Items]            
Principal value $ 350,000,000   $ 350,000,000      
Proceeds from issuance of senior notes, net of discount and issuance cost     345,000,000      
Payments for settlement of 3.875% Convertible Notes     $ 250,000,000      
Debt Instrument, Redemption Price 358,400,000          
Redemption Premium $ 9,000,000.0          
Senior Notes | 3.50% Senior Notes            
Debt Instrument [Line Items]            
Principal value       350,000,000    
Long-term debt       347,987,000 347,639,000  
Senior Notes | 5.375% Senior Notes            
Debt Instrument [Line Items]            
Long-term debt       $ 0 $ 348,826,000