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Shareholders' Equity - Participating Preferred Shares (Details)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
market
Class of Stock [Line Items]    
Cumulative change in value of index based on purchase prices (as a percent)   50.00%
Number of top markets used for purchase price index | market   20
Liquidation preference value | $ $ 480.0 $ 480.0
5.0% Series A Participating Preferred Shares    
Class of Stock [Line Items]    
Preferred stock, dividend rate, percentage 5.00% 5.00%
5.0% Series B Participating Preferred Shares    
Class of Stock [Line Items]    
Preferred stock, dividend rate, percentage 5.00% 5.00%
5.5% Series C Participating Preferred Shares    
Class of Stock [Line Items]    
Preferred stock, dividend rate, percentage 5.50% 5.50%