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Shareholders' Equity (Details) - USD ($)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Feb. 12, 2018
Dec. 31, 2018
Oct. 30, 2018
Oct. 29, 2018
Nov. 29, 2017
Apr. 25, 2017
Distribution Made to Limited Partner [Line Items]                
Authorized stock repurchase amount               $ 250,000,000.0
Remaining unused authorization for stock repurchase program           $ 78,300,000    
Repurchase aggregate cost $ 32,600,000 $ 514,400,000            
Repurchase of common stock included in accrued expenses 1,000,000.0 $ 0            
October 2018 Stock Repurchase Program                
Distribution Made to Limited Partner [Line Items]                
Authorized stock repurchase amount         $ 300,000,000.0      
Remaining unused authorization for stock repurchase program $ 243,000,000.0              
Repurchase of common stock (in shares) 282,416              
Repurchase aggregate cost $ 25,000,000.0              
Repurchase of common stock included in accrued expenses $ 1,000,000.0     $ 2,500,000        
Shares of common stock repurchase 79,233              
Shares of common stock repurchased $ 7,600,000              
Tender Offer                
Distribution Made to Limited Partner [Line Items]                
Authorized stock repurchase amount             $ 500,000,000.0  
Repurchase of common stock (in shares)     5,660,376          
Repurchase aggregate cost     $ 500,000,000.0          
Repurchase price (in dollars per share)     $ 88.33