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Shareholders' Equity / Partners' Capital - Participating Preferred Shares (Details) $ / shares in Units, $ in Millions |  | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | ---
Oct. 03, 2017 market $ / shares shares | Dec. 31, 2017 USD ($) | Sep. 30, 2017 USD ($) $ / shares shares | Sep. 30, 2016 | Sep. 30, 2017 USD ($) market $ / shares shares | Mar. 31, 2017 $ / shares | Dec. 31, 2016 $ / shares shares
Class of Stock [Line Items] |  |  |  |  |  |  |
Cumulative change in value of index based on purchase prices |  |  |  |  | 50.00% |  |
Number of top markets used for purchase price index | market |  |  |  |  | 20 |  |
Liquidation preference value | $ |  |  | $ 490.7 |  | $ 490.7 |  |
Preferred shares, shares outstanding (in shares) |  |  | 47,810,000 |  | 47,810,000 |  | 37,010,000
Subsequent Event |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Issuance of common shares, net of offering costs (in shares) | 12,398,276 |  |  |  |  |  |
Class A conversion ratio | 1.3106 |  |  |  |  |  |
5.0% Series A Participating Preferred Shares |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Preferred stock, dividend rate, percentage |  |  | 5.00% | 5.00% | 5.00% |  |
5.0% Series A Participating Preferred Shares | Subsequent Event |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Preferred stock, dividend rate, percentage | 5.00% |  |  |  |  |  |
Preferred shares, shares outstanding (in shares) | 5,060,000 |  |  |  |  |  |
5.0% Series B Participating Preferred Shares |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Preferred stock, dividend rate, percentage |  |  | 5.00% | 5.00% | 5.00% |  |
5.0% Series B Participating Preferred Shares | Subsequent Event |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Preferred stock, dividend rate, percentage | 5.00% |  |  |  |  |  |
Preferred shares, shares outstanding (in shares) | 4,400,000 |  |  |  |  |  |
5.5% Series C Participating Preferred Shares |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Preferred stock, dividend rate, percentage |  |  | 5.50% | 5.50% | 5.50% |  |
Class A common shares/units |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Common shares, par value (in dollars per share) | $ / shares |  |  | $ 0.01 |  | $ 0.01 | $ 0.01 | $ 0.01
Class A common shares/units | Scenario, Forecast |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Allocation to participating preferred shareholders | $ |  | $ 27.6 |  |  |  |  |
Class A common shares/units | Subsequent Event |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Common shares, par value (in dollars per share) | $ / shares | $ 0.01 |  |  |  |  |  |
Percent of liquidation preference | 50.00% |  |  |  |  |  |
Number of markets used in calculation of conversion ratio | market | 20 |  |  |  |  |  |

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