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Equity (Details) - USD ($) $ in Millions | 6 Months Ended
--- | ---
Jun. 30, 2018 | Jun. 30, 2017
Class of Stock [Line Items] |  |
Conversion of common units to common shares (in units/shares) | 53,817 | 187,000
Forward Equity Sale Agreement |  |
Class of Stock [Line Items] |  |
Proceeds from common shares issued under forward equity sale agreements | $ 52.3 |
Forward Equity Sale Agreement | Common Shares |  |
Class of Stock [Line Items] |  |
Number of shares issued | 1,800,000 |
Remaining capacity under forward equity sale agreements | 5,700,000 |
Common Stock Issued to Public Under At-the-Market Program | Common Shares |  |
Class of Stock [Line Items] |  |
At-market stock, offering program established, remaining capacity | $ 70.0 |

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