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Capital Stock - Narrative (Details)
 9 Months Ended
Sep. 30, 2017
USD ($)
$ / shares
shares
Dec. 31, 2016
$ / shares
shares
Class of Stock [Line Items]    
Common stock, shares authorized (up to) | shares 400,000,000 400,000,000
Common stock, par value (in dollars per share) | $ / shares $ 0.01 $ 0.01
Remaining capacity | $ $ 143,500,000  
Preferred stock, shares authorized (up to) | shares 10,000,000 10,000,000
Preferred stock, par value (in dollars per share) | $ / shares $ 0.01 $ 0.01
Preferred stock, shares outstanding | shares 0 0
Common stock partnership units option redemption ratio 1  
Common Stock    
Class of Stock [Line Items]    
Aggregate offering price (up to) | $ $ 200,000,000  
Remaining amount under ATM program | $ 128,300,000  
Value amount of shares authorized to be repurchased (up to) | $ $ 150,000,000  
Unaffiliated Third Parties    
Class of Stock [Line Items]    
Operating partnerships units held (in shares) | shares 0 0