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Shareholders' Equity - Class A Common Share Offering (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2017
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2016
Class of Stock [Line Items]        
Proceeds from issuance of shares   $ 355,589 $ 2  
Stock issuance costs   $ 350 $ 0  
Class A common shares        
Class of Stock [Line Items]        
Common shares, par value (in dollars per share)   $ 0.01   $ 0.01
Underwritten Public Offering | Class A common shares        
Class of Stock [Line Items]        
Shares issued during period (in shares) 14,842,982      
Common shares, par value (in dollars per share) $ 0.01      
Proceeds from issuance of shares $ 336,500      
Stock issuance costs $ 400