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Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified | 0 Months Ended | 3 Months Ended
--- | --- | ---
Mar. 19, 2013 | Mar. 31, 2013 | Mar. 31, 2012
Common Shares |  |  |
Shares issued to the public (in shares) | 4,485,000 |  |
Shares issued to the public (in dollars per share) | $ 26.34 |  |
Public Offering, Proceeds After Underwriter Discounts But Before Offering Expenses | $ 118,100 | $ 117,913 |
Number of operating parterships units converted into common shares (in units) |  | 248,644 | 34,550
Number of common shares for each converted common unit (in shares) |  | 1 |

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