Quarterly report pursuant to Section 13 or 15(d)

Equity (Details)

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Equity (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended
Jun. 27, 2017
Jan. 21, 2017
Jun. 30, 2017
Dec. 31, 2016
Jun. 30, 2017
Jun. 30, 2016
Class of Stock [Line Items]            
Redemption of preferred shares (6,900,000 shares)         $ 172,500  
Conversion of common units to common shares (in units/shares)         187,000 26,758
Common Stock Issued to Public Under At-the-Market Program            
Class of Stock [Line Items]            
Shares issued to the public (in shares)         591,042  
Issuance of stock, weighted average price per share (in dollars per share)         $ 33.84  
Net proceeds from shares issued         $ 19,700  
Payments of stock issuance costs         300  
At-market stock, offering program established, remaining capacity     $ 70,000   $ 70,000  
Series K Cumulative Preferred Stock            
Class of Stock [Line Items]            
Dividend rate (percent)   5.60%        
Preferred stock, redemption price per share (in dollars per share)   $ 50.00        
Redemption of preferred shares (6,900,000 shares)   $ 26,600        
Issuance costs associated with redeemed preferred shares       $ 17    
Series L Cumulative Preferred Stock            
Class of Stock [Line Items]            
Dividend rate (percent) 7.375%          
Preferred stock, redemption price per share (in dollars per share) $ 25.00          
Redemption of preferred shares (6,900,000 shares) $ 172,500          
Issuance costs associated with redeemed preferred shares     $ 6,800