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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 |  |  |

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